T. Sherry, C. Kent, Natalie V. Sánchez, Ç. Şekercioğlu
ABSTRACT Insectivorous birds reach their highest diversity in the tropics and represent a striking variety of morphological and behavioral specializations for foraging, yet explanations for these patterns are inadequate because of both our limited understanding of the drivers of ecological diversification within and among clades and of coexistence mechanisms in particular. Here we synthesize recent information on Neotropical insectivorous birds, including their diversity, evolutionary ages and locations of origin, phylogenies, and both competitive and predator–prey species interactions. We propose a novel evolutionary hypothesis for the origin and coexistence of the phenotypic diversity of insectivore foraging morphologies in species-rich communities, based on their extraordinary food-resource specializations. Specifically, we develop the Biotic Challenge Hypothesis to explain the evolution of these specializations, and we provide preliminary evidence in support of this hypothesis based on a synopsis of both Neotropical insectivore specializations by family and arthropod antipredator adaptations by category. We argue that, from the perspective of tropical insectivorous birds, and particularly in the most species-rich, mainland Neotropical communities, the environment is an arthropod desert. Coexistence with all of the other insectivores requires feeding specialization to compete exploitatively and diffusely against evolutionarily diverse species and far less frequently against sister species. The arthropod desert arises primarily because of (1) the tactical diversity of arthropod predators as insectivore competitors and (2) the evolutionary arms races involving arthropod predators with their prey, which render many arthropods inaccessible to most insectivorous predators. Our idea provides an explicit mechanism for pervasive, diffuse tropical interspecific competition, for evolutionary specialization, and for positive feedback on speciation rates at low latitudes, thereby generating new predictions and insights into tropical life histories and the Latitudinal Diversity Gradient. Other recent ideas concerning the coexistence of Neotropical insectivores, including positive species interactions within mixed species flocks, are recognized and evaluated. We discuss ways to test predictions resulting from the new view of communities developed here, including a case study of diet specialization by Costa Rican tyrannid flycatchers. Our synthesis of the origin and nature of Neotropical insectivore communities injects new life into the “zombie” idea that evolution works differently in the species-rich tropics. LAY SUMMARY New World tropical (Neotropical) insectivorous bird communities are extremely rich in species. These birds are also extraordinarily diverse in how they forage, and illustrate a variety of specializations, but why? This paper summarizes and integrates information on the evolution of the diverse Neotropical avifauna, interspecific competitio
{"title":"Insectivorous birds in the Neotropics: Ecological radiations, specialization, and coexistence in species-rich communities","authors":"T. Sherry, C. Kent, Natalie V. Sánchez, Ç. Şekercioğlu","doi":"10.1093/auk/ukaa049","DOIUrl":"https://doi.org/10.1093/auk/ukaa049","url":null,"abstract":"ABSTRACT Insectivorous birds reach their highest diversity in the tropics and represent a striking variety of morphological and behavioral specializations for foraging, yet explanations for these patterns are inadequate because of both our limited understanding of the drivers of ecological diversification within and among clades and of coexistence mechanisms in particular. Here we synthesize recent information on Neotropical insectivorous birds, including their diversity, evolutionary ages and locations of origin, phylogenies, and both competitive and predator–prey species interactions. We propose a novel evolutionary hypothesis for the origin and coexistence of the phenotypic diversity of insectivore foraging morphologies in species-rich communities, based on their extraordinary food-resource specializations. Specifically, we develop the Biotic Challenge Hypothesis to explain the evolution of these specializations, and we provide preliminary evidence in support of this hypothesis based on a synopsis of both Neotropical insectivore specializations by family and arthropod antipredator adaptations by category. We argue that, from the perspective of tropical insectivorous birds, and particularly in the most species-rich, mainland Neotropical communities, the environment is an arthropod desert. Coexistence with all of the other insectivores requires feeding specialization to compete exploitatively and diffusely against evolutionarily diverse species and far less frequently against sister species. The arthropod desert arises primarily because of (1) the tactical diversity of arthropod predators as insectivore competitors and (2) the evolutionary arms races involving arthropod predators with their prey, which render many arthropods inaccessible to most insectivorous predators. Our idea provides an explicit mechanism for pervasive, diffuse tropical interspecific competition, for evolutionary specialization, and for positive feedback on speciation rates at low latitudes, thereby generating new predictions and insights into tropical life histories and the Latitudinal Diversity Gradient. Other recent ideas concerning the coexistence of Neotropical insectivores, including positive species interactions within mixed species flocks, are recognized and evaluated. We discuss ways to test predictions resulting from the new view of communities developed here, including a case study of diet specialization by Costa Rican tyrannid flycatchers. Our synthesis of the origin and nature of Neotropical insectivore communities injects new life into the “zombie” idea that evolution works differently in the species-rich tropics. LAY SUMMARY New World tropical (Neotropical) insectivorous bird communities are extremely rich in species. These birds are also extraordinarily diverse in how they forage, and illustrate a variety of specializations, but why? This paper summarizes and integrates information on the evolution of the diverse Neotropical avifauna, interspecific competitio","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114637683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Rohwer, Vanya G. Rohwer, M. Sethi, J. HilleRisLambers
ABSTRACT Using the patterns of fault bars in their primaries, we studied the mode of primary replacement in non-molting Lesser Sandhill Cranes (Antigone c. canadensis) salvaged from hunters in southwestern Saskatchewan. About 80% of their primaries are used for 2 yr and 20% for 3 yr. Primaries are replaced during the breeding season and are lost in synchronous blocks representing about half the primaries, suggesting that most adults probably can fly weakly during flight feather replacement. Cranes are large, aggressive birds, and this interesting, and undescribed mode of flight feather replacement seems adapted to the ability of adult cranes to defend their precocial chicks from predators. Strikingly, juvenile Sandhill Cranes showed no fault marks in their primaries, suggesting that their parents' ability to protect them shields them from the fright of predator attacks, which, in most birds, causes fault bars to be more prevalent and strongly expressed in juveniles than adults. Adults show interesting variation in the number of primaries replaced annually, which seems likely related to whether or not they are caring for chicks. Further, single primaries may or may not be replaced preferentially, suggesting sensitivity to feather function. Evaluating these observations must await field studies of molting adults. LAY SUMMARY Lesser Sandhill Cranes that breed in the far north replace about half of their primaries annually in a synchronous molt This resolves 2 time period conflicts: the exponential increase with body size in the time required to molt, and the need to overlap primary molt with parental care. Using fault marks, feather growth rates, and feather wear, we deciphered this previously unknown mode of primary replacement from a sample of non-molting birds. Within adjacent blocks of same-age primaries, distance differences from feather tip to marker faults showed that feather pairs were usually lost within 24 hr of each other. Cranes are big, tough birds, and synchronous loss of about half of the primaries helps parents defend young from formidable predators. Synchronous replacement also reduces molt duration to the time required to grow the longest renewed primary, squeezing primary renewal of this far-northern breeder into the brief time window before their long southward migration.
摘要/ ABSTRACT摘要:利用初级断层的模式，研究了在萨斯喀彻温省西南部从猎人手中打捞到的未脱毛的小沙丘鹤(Antigone c. canadensis)的初级替换模式。大约80%的原毛用于2年，20%用于3年。在繁殖季节，原毛会被替换，并在大约一半的原毛中同步丢失，这表明大多数成年鸟可能在更换飞羽期间飞行能力较弱。鹤是一种大型的、具有攻击性的鸟类，这种有趣的、未被描述过的飞行羽毛替换模式似乎适应了成年鹤保护早熟雏鸟免受捕食者伤害的能力。引人注目的是，幼年沙丘鹤在它们的初级阶段没有显示出错误标记，这表明它们的父母有能力保护它们免受捕食者的攻击，这在大多数鸟类中导致错误标记在幼年中比成年鸟类更普遍和强烈地表达出来。成年鸟在每年更换初级鸟的数量上表现出有趣的变化，这似乎与它们是否照顾雏鸟有关。此外，单一的原色可能会被优先替换，也可能不会，这表明对羽毛功能的敏感性。评估这些观察结果必须等待对蜕皮成虫的实地研究。在遥远的北方繁殖的小沙丘鹤每年在一次同步蜕皮中更换大约一半的初级蜕皮，这解决了两个时间冲突:蜕皮所需的时间随着身体尺寸的指数增长，以及需要将初级蜕皮与父母照顾重叠。利用缺陷标记、羽毛生长速率和羽毛磨损，我们从非换羽鸟类的样本中破译了这种以前未知的初级替换模式。在邻近的同年龄初级岩块中，从羽毛尖端到标记断层的距离差异表明，羽毛对通常在24小时内丢失。鹤是一种体型庞大、身体强壮的鸟类，同时失去大约一半的初级能力有助于父母保护孩子免受可怕的捕食者的伤害。同步替换也减少了蜕皮持续时间，使长出最长的更新初级所需的时间，将这个遥远的北方繁殖者的初级更新压缩到它们向南迁徙之前的短暂时间窗口。
{"title":"Life-history implications of migratory Lesser Sandhill Cranes replacing adjacent blocks of primaries synchronously","authors":"S. Rohwer, Vanya G. Rohwer, M. Sethi, J. HilleRisLambers","doi":"10.1093/auk/ukaa058","DOIUrl":"https://doi.org/10.1093/auk/ukaa058","url":null,"abstract":"ABSTRACT Using the patterns of fault bars in their primaries, we studied the mode of primary replacement in non-molting Lesser Sandhill Cranes (Antigone c. canadensis) salvaged from hunters in southwestern Saskatchewan. About 80% of their primaries are used for 2 yr and 20% for 3 yr. Primaries are replaced during the breeding season and are lost in synchronous blocks representing about half the primaries, suggesting that most adults probably can fly weakly during flight feather replacement. Cranes are large, aggressive birds, and this interesting, and undescribed mode of flight feather replacement seems adapted to the ability of adult cranes to defend their precocial chicks from predators. Strikingly, juvenile Sandhill Cranes showed no fault marks in their primaries, suggesting that their parents' ability to protect them shields them from the fright of predator attacks, which, in most birds, causes fault bars to be more prevalent and strongly expressed in juveniles than adults. Adults show interesting variation in the number of primaries replaced annually, which seems likely related to whether or not they are caring for chicks. Further, single primaries may or may not be replaced preferentially, suggesting sensitivity to feather function. Evaluating these observations must await field studies of molting adults. LAY SUMMARY Lesser Sandhill Cranes that breed in the far north replace about half of their primaries annually in a synchronous molt This resolves 2 time period conflicts: the exponential increase with body size in the time required to molt, and the need to overlap primary molt with parental care. Using fault marks, feather growth rates, and feather wear, we deciphered this previously unknown mode of primary replacement from a sample of non-molting birds. Within adjacent blocks of same-age primaries, distance differences from feather tip to marker faults showed that feather pairs were usually lost within 24 hr of each other. Cranes are big, tough birds, and synchronous loss of about half of the primaries helps parents defend young from formidable predators. Synchronous replacement also reduces molt duration to the time required to grow the longest renewed primary, squeezing primary renewal of this far-northern breeder into the brief time window before their long southward migration.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121766409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT Functional diversity (FD) approaches have been increasingly used to understand ecosystem functioning in bird communities. These approaches typically rely on the assumption that species are perfectly detected in the field, despite the fact that imperfect detection represents a ubiquitous source of bias in biodiversity studies. This may be notably important in FD studies, because detection may depend on the functional traits used to compute FD metrics. However, little effort has been devoted to account for imperfect detection in FD studies, and therefore the degree to which species traits and detectability affects FD remains poorly understood. We predict that observed FD metrics may either underestimate or overestimate detection-corrected FD, because FD has multiple independent dimensions with different data properties. We assessed whether detection was related to bird traits (body mass, diet, and foraging stratum), accounting for habitat type, season, and phylogeny. We then used a multi-species occupancy model to obtain detection-corrected FD metrics (functional richness [FRic], functional evenness [FEve], and functional divergence [FDiv]), and compared observed and detection-corrected FD estimates in bird communities from east-central Argentina. Some functional types of birds (raptors and insectivores) were more easily overlooked, whereas others (seed and leaf eaters) were more easily detected. Some observed FD metrics underestimated detection-corrected FD (FRic and FDiv), whereas some others (FEve) overestimated detection-corrected FD. Both observed and detection-corrected FRic revealed differences between seasons, but not between habitat types. However, detection-corrected FEve and FDiv showed differences between seasons, contrary to observed estimates. Our results indicate that failure to account for unequal ease of detecting species can lead to erroneous estimates of FD because some functional types of birds are more easily overlooked. We outline some guidelines to help ornithologists identifying under which circumstances detection may be a concern and warn against the indiscriminate use of FD metrics without accounting for species detection. LAY SUMMARY Functional diversity relies on the assumption of perfect species detection, but how species traits affect detection remains poorly understood. We compared observed and detection-corrected functional diversity in bird communities. Some functional types of birds were more easily overlooked than others, biasing functional diversity metrics. Bird diet represented a functional trait accounting for imperfect detection. Seed and leaf eaters were more easily detected; raptors and insectivores were more easily overlooked. Observed functional diversity indices either underestimated or overestimated detection-corrected functional diversity metrics. Failure to account for unequal ease of detecting species can lead to erroneous estimates of functional diversity because some functional types of bi
{"title":"The costs of ignoring species detectability on functional diversity estimation","authors":"F. X. Palacio, René E. Maragliano, D. Montalti","doi":"10.1093/auk/ukaa057","DOIUrl":"https://doi.org/10.1093/auk/ukaa057","url":null,"abstract":"ABSTRACT Functional diversity (FD) approaches have been increasingly used to understand ecosystem functioning in bird communities. These approaches typically rely on the assumption that species are perfectly detected in the field, despite the fact that imperfect detection represents a ubiquitous source of bias in biodiversity studies. This may be notably important in FD studies, because detection may depend on the functional traits used to compute FD metrics. However, little effort has been devoted to account for imperfect detection in FD studies, and therefore the degree to which species traits and detectability affects FD remains poorly understood. We predict that observed FD metrics may either underestimate or overestimate detection-corrected FD, because FD has multiple independent dimensions with different data properties. We assessed whether detection was related to bird traits (body mass, diet, and foraging stratum), accounting for habitat type, season, and phylogeny. We then used a multi-species occupancy model to obtain detection-corrected FD metrics (functional richness [FRic], functional evenness [FEve], and functional divergence [FDiv]), and compared observed and detection-corrected FD estimates in bird communities from east-central Argentina. Some functional types of birds (raptors and insectivores) were more easily overlooked, whereas others (seed and leaf eaters) were more easily detected. Some observed FD metrics underestimated detection-corrected FD (FRic and FDiv), whereas some others (FEve) overestimated detection-corrected FD. Both observed and detection-corrected FRic revealed differences between seasons, but not between habitat types. However, detection-corrected FEve and FDiv showed differences between seasons, contrary to observed estimates. Our results indicate that failure to account for unequal ease of detecting species can lead to erroneous estimates of FD because some functional types of birds are more easily overlooked. We outline some guidelines to help ornithologists identifying under which circumstances detection may be a concern and warn against the indiscriminate use of FD metrics without accounting for species detection. LAY SUMMARY Functional diversity relies on the assumption of perfect species detection, but how species traits affect detection remains poorly understood. We compared observed and detection-corrected functional diversity in bird communities. Some functional types of birds were more easily overlooked than others, biasing functional diversity metrics. Bird diet represented a functional trait accounting for imperfect detection. Seed and leaf eaters were more easily detected; raptors and insectivores were more easily overlooked. Observed functional diversity indices either underestimated or overestimated detection-corrected functional diversity metrics. Failure to account for unequal ease of detecting species can lead to erroneous estimates of functional diversity because some functional types of bi","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128251682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Lees, K. Rosenberg, V. Ruiz‐Gutierrez, S. Marsden, T. Schulenberg, A. Rodewald
ABSTRACT Securing the long-term resilience of the world's most speciose avifauna, that of the Neotropics, requires spatially and temporally explicit data to inform decisions. We examine gaps in our knowledge of the region's avifauna through the lens of the biodiversity shortfall concept: the gaps between realized knowledge and complete knowledge. This framework serves as a useful tool to take stock of the last 25 yr of Neotropical ornithological work since the untimely death of Ted Parker. Here, we highlight 7 key shortfalls: taxonomy, distribution, abundance, evolutionary patterns, abiotic tolerances, species traits, and biotic interactions. We then propose an eighth—and new—“Parkerian” shortfall that reflects a lack of basic natural history knowledge key to understanding how species might respond to environmental challenges. Bridging this shortfall will help reverse declines by informing reintroduction, recovery network, and habitat restoration efforts. We discuss the challenges imposed by each shortfall and how strategies such as citizen-science initiatives and technological advances can either remedy or mitigate the uncertainty they generate.
{"title":"A roadmap to identifying and filling shortfalls in Neotropical ornithology","authors":"A. Lees, K. Rosenberg, V. Ruiz‐Gutierrez, S. Marsden, T. Schulenberg, A. Rodewald","doi":"10.1093/auk/ukaa048","DOIUrl":"https://doi.org/10.1093/auk/ukaa048","url":null,"abstract":"ABSTRACT Securing the long-term resilience of the world's most speciose avifauna, that of the Neotropics, requires spatially and temporally explicit data to inform decisions. We examine gaps in our knowledge of the region's avifauna through the lens of the biodiversity shortfall concept: the gaps between realized knowledge and complete knowledge. This framework serves as a useful tool to take stock of the last 25 yr of Neotropical ornithological work since the untimely death of Ted Parker. Here, we highlight 7 key shortfalls: taxonomy, distribution, abundance, evolutionary patterns, abiotic tolerances, species traits, and biotic interactions. We then propose an eighth—and new—“Parkerian” shortfall that reflects a lack of basic natural history knowledge key to understanding how species might respond to environmental challenges. Bridging this shortfall will help reverse declines by informing reintroduction, recovery network, and habitat restoration efforts. We discuss the challenges imposed by each shortfall and how strategies such as citizen-science initiatives and technological advances can either remedy or mitigate the uncertainty they generate.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121474603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT Eggshell pigmentation is generated by 2 major pigments, biliverdin and protoporphyrin. The latter is mostly deposited in red, brown, and black egg spots and it has been hypothesized that greater expression of egg spottiness (as measured by the number, area, and coloration of spots) may act as an honest signal of female quality for males (sexual signaling hypothesis, SSH). The important assumption of the SSH is that eggshell pigmentation correlates with phenotypic and genetic components of female quality, although phenotypic quality of females may also be under environmental control. The aim of this study was to test for the associations of protoporphyrin-based egg pigmentation with both phenotypic and genetic female traits and environmental variables (microhabitat and urbanization) in a common rallid species, the Eurasian Coot (Fulica atra). We found that the total number of egg spots was positively associated with female condition (size-corrected body mass) and expression of a putative bare-part ornament (frontal shield). The same measure of spottiness negatively correlated with the level of physiological stress in females. No evidence was found for associations between egg spottiness and genetic traits in females (neutral heterozygosity and polymorphism of pathogen recognition receptors, the Major Histocompatibility Complex), but there was a linear increase in the expression of egg spottiness over the breeding season, which may suggest that it is regulated by food availability. Our study indicates that protoporphyrin-based pigmentation of eggs reflects female phenotypic traits (condition, stress, and ornament expression) in the Eurasian Coot, although it remains to be established whether it plays any signaling role and whether it is driven by sexual selection in this species. LAY SUMMARY There is equivocal support for direct associations between maternal quality and deposition of protoporphyrin pigmentation (dark spots and blotches) in avian eggshells. Research on protoporphyrin eggshell pigmentation has primarily focused on a single avian order (Passeriformes). We examined associations of protoporphyrin-based eggshell pigmentation with female phenotypic and genetic traits in a non-passerine species, the Eurasian Coot. Deposition of protoporphyrin in eggshells (total number per area of egg spots) positively correlated with female condition and expression of a putative bare-part ornament (frontal shield), while it was negatively associated with the level of physiological stress. Protoporphyrin-based eggshell pigmentation acts as a reliable signal of female phenotypic (but not genetic) traits in the Eurasian Coot. Signaling properties of protoporphyrin-based egg coloration are likely to largely differ between different evolutionary lineages of birds.
{"title":"Egg spottiness reflects female condition, physiological stress, and ornament expression in a common rallid species","authors":"P. Minias, J. Gómez, R. Włodarczyk","doi":"10.1093/auk/ukaa054","DOIUrl":"https://doi.org/10.1093/auk/ukaa054","url":null,"abstract":"ABSTRACT Eggshell pigmentation is generated by 2 major pigments, biliverdin and protoporphyrin. The latter is mostly deposited in red, brown, and black egg spots and it has been hypothesized that greater expression of egg spottiness (as measured by the number, area, and coloration of spots) may act as an honest signal of female quality for males (sexual signaling hypothesis, SSH). The important assumption of the SSH is that eggshell pigmentation correlates with phenotypic and genetic components of female quality, although phenotypic quality of females may also be under environmental control. The aim of this study was to test for the associations of protoporphyrin-based egg pigmentation with both phenotypic and genetic female traits and environmental variables (microhabitat and urbanization) in a common rallid species, the Eurasian Coot (Fulica atra). We found that the total number of egg spots was positively associated with female condition (size-corrected body mass) and expression of a putative bare-part ornament (frontal shield). The same measure of spottiness negatively correlated with the level of physiological stress in females. No evidence was found for associations between egg spottiness and genetic traits in females (neutral heterozygosity and polymorphism of pathogen recognition receptors, the Major Histocompatibility Complex), but there was a linear increase in the expression of egg spottiness over the breeding season, which may suggest that it is regulated by food availability. Our study indicates that protoporphyrin-based pigmentation of eggs reflects female phenotypic traits (condition, stress, and ornament expression) in the Eurasian Coot, although it remains to be established whether it plays any signaling role and whether it is driven by sexual selection in this species. LAY SUMMARY There is equivocal support for direct associations between maternal quality and deposition of protoporphyrin pigmentation (dark spots and blotches) in avian eggshells. Research on protoporphyrin eggshell pigmentation has primarily focused on a single avian order (Passeriformes). We examined associations of protoporphyrin-based eggshell pigmentation with female phenotypic and genetic traits in a non-passerine species, the Eurasian Coot. Deposition of protoporphyrin in eggshells (total number per area of egg spots) positively correlated with female condition and expression of a putative bare-part ornament (frontal shield), while it was negatively associated with the level of physiological stress. Protoporphyrin-based eggshell pigmentation acts as a reliable signal of female phenotypic (but not genetic) traits in the Eurasian Coot. Signaling properties of protoporphyrin-based egg coloration are likely to largely differ between different evolutionary lineages of birds.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130922018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT Following copulation, females of many seabird species spend a prolonged period of time away from the colony, building up reserves for egg formation and incubation. Here, we report that the number of sperm associated with eggs of single-egg clutch seabirds was almost an order of magnitude greater than predicted from the relationship between ovum size and sperm numbers in multi-egg clutch non-seabirds. Sperm numbers were also several times greater than the estimated number necessary for maximal fertilization success. Our results are consistent with 3 unusual features of seabird reproduction: (1) single-egg clutches, (2) prolonged sperm storage, and (3) a lag period between the end of yolk formation and ovulation. We hypothesize that sperm release from storage is under precise temporal control in these species, with high sperm numbers acting as an insurance against infertility in single-egg clutches. If true, the lag period may have evolved to provide sufficient time for sperm to be released simultaneously from storage and accumulate at the site of fertilization prior to ovulation. LAY SUMMARY After copulation, female birds store sperm in their reproductive systems for some time before egg production and fertilization. It is thought that sperm are gradually lost during storage, meaning that later in the storage period, if there are no further inseminations, fewer sperm should be available for insemination. We studied the number of sperm reaching eggs in 6 seabird species, in which females spend a long time feeding at sea between mating and producing eggs. Surprisingly, we found that the number of sperm that reached eggs in these species was much higher than expected, based on a known relationship between egg size and sperm number. We suggest that, in these species, sperm are released simultaneously from storage just before ovulation. This may be particularly important in the species we studied, because they all lay only a single egg. Our hypothesis implies that female birds have greater control over sperm storage and use than previously thought.
{"title":"Extraordinary sperm to egg ratios in seabirds","authors":"N. Hemmings, T. Birkhead","doi":"10.1093/auk/ukaa052","DOIUrl":"https://doi.org/10.1093/auk/ukaa052","url":null,"abstract":"ABSTRACT Following copulation, females of many seabird species spend a prolonged period of time away from the colony, building up reserves for egg formation and incubation. Here, we report that the number of sperm associated with eggs of single-egg clutch seabirds was almost an order of magnitude greater than predicted from the relationship between ovum size and sperm numbers in multi-egg clutch non-seabirds. Sperm numbers were also several times greater than the estimated number necessary for maximal fertilization success. Our results are consistent with 3 unusual features of seabird reproduction: (1) single-egg clutches, (2) prolonged sperm storage, and (3) a lag period between the end of yolk formation and ovulation. We hypothesize that sperm release from storage is under precise temporal control in these species, with high sperm numbers acting as an insurance against infertility in single-egg clutches. If true, the lag period may have evolved to provide sufficient time for sperm to be released simultaneously from storage and accumulate at the site of fertilization prior to ovulation. LAY SUMMARY After copulation, female birds store sperm in their reproductive systems for some time before egg production and fertilization. It is thought that sperm are gradually lost during storage, meaning that later in the storage period, if there are no further inseminations, fewer sperm should be available for insemination. We studied the number of sperm reaching eggs in 6 seabird species, in which females spend a long time feeding at sea between mating and producing eggs. Surprisingly, we found that the number of sperm that reached eggs in these species was much higher than expected, based on a known relationship between egg size and sperm number. We suggest that, in these species, sperm are released simultaneously from storage just before ovulation. This may be particularly important in the species we studied, because they all lay only a single egg. Our hypothesis implies that female birds have greater control over sperm storage and use than previously thought.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125400005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jon Edward Ahlquist died on May 7, 2020, at the age of 75. Thirty years ago, Jon was one of the most famous ornithologists in the world, co-recipient of the 1988 Daniel Giraud Elliot Medal from the National Academy of Sciences and winner of the 1983 Edward’s Prize from the Wilson Ornithological Society. He was also an outstanding bird watcher, artist, and photographer. Yet few ornithologists ever met Jon, let alone knew him as a colleague or friend. He rarely attended American Ornithologists’ Union (AOU) or other scientific meetings, he was not an Elective Member or Fellow of the AOU, and he disappeared from mainstream academia in 1994, only to reemerge in 2017 as a scientific spokesperson for Creationism (https://creation.com/jon-ahlquist). Even for those of us who knew him, Jon was largely an enigma, in many ways open and giving but in others private and almost mysterious. We all realized, however, that Jon was a brilliant intellectual with an encyclopedic knowledge of birds, art, classical music, language, food, photography, and more. He could be hysterically funny, shockingly profane, and outrageous in dress and lifestyle. Although he played a pioneering role in the development of molecular systematics, no one outside a small circle of colleagues knew what he actually did because he never promoted himself publicly and was completely overshadowed and dominated by his mentor and partner of 28 years, Charles G. Sibley. Jon was born on July 27, 1944, the only child of Lula and Arvid Ahlquist. He was raised speaking Finnish in Ashtabula, Ohio, on the edge of Lake Erie, where he developed his bird watching and artistic skills. He had a major showing of his paintings at age 14 and published his first paper (a breeding bird census) at 16. At Ashtabula High School Jon was president of the National Honor Society, editor of the school newspaper, art editor for the yearbook, and valedictorian. Upon graduation, in 1962, he headed to Cornell, drawn not only to its ornithology program but also by Cornell’s historic role in American bird art. Upon arrival, Jon found himself rubbing elbows with such illustrious undergraduates as James Brown and Douglas Futuyma, and postgrads Alan Brush, Joanna Burger, Kendall Corbin, Herb Hendrickson, and Neal Smith. As soon as he arrived, Jon sought out Charles Sibley, who was at that time a renowned professor of zoology. His arrival in Sibley’s lab was described in a 2011 email from Neal Smith to Kevin Winker:
乔恩·爱德华·阿尔奎斯特于2020年5月7日去世，享年75岁。三十年前，乔恩是世界上最著名的鸟类学家之一，1988年美国国家科学院丹尼尔·吉拉德·埃利奥特奖章的共同获得者，1983年威尔逊鸟类学会爱德华奖的获得者。他还是一位杰出的观鸟者、艺术家和摄影师。然而，很少有鸟类学家见过乔恩，更不用说把他当作同事或朋友了。他很少参加美国鸟类学家联盟(AOU)或其他科学会议，他不是AOU的选举成员或研究员，他于1994年从主流学术界消失，直到2017年才以神创论的科学发言人的身份重新出现(https://creation.com/jon-ahlquist)。即使对我们这些认识他的人来说，乔恩在很大程度上也是一个谜，在许多方面，他是开放的，给予的，但在其他方面，他是私密的，几乎是神秘的。然而，我们都意识到，乔恩是一个才华横溢的知识分子，对鸟类、艺术、古典音乐、语言、食物、摄影等方面都有渊博的知识。他可以歇斯底里地搞笑，令人震惊地亵渎，在穿着和生活方式上令人发指。尽管他在分子系统学的发展中发挥了先锋作用，但除了一小群同事之外，没有人知道他到底做了什么，因为他从未公开推销自己，而且完全被他28年的导师和合作伙伴查尔斯·g·西布里(Charles G. Sibley)所掩盖和支配。乔恩出生于1944年7月27日，是卢拉和阿维德·阿尔奎斯特的独子。他在俄亥俄州伊利湖边上的阿什塔布拉长大，说芬兰语，在那里他培养了观鸟和艺术技能。14岁时，他举办了一次大型画展，16岁时发表了第一篇论文(繁殖鸟类普查)。在阿什塔布拉高中，乔恩是全国荣誉协会的主席，校报的编辑，年鉴的美术编辑，以及致告别辞的代表。1962年毕业后，他前往康奈尔大学，不仅被其鸟类学项目所吸引，也被康奈尔大学在美国鸟类艺术领域的历史地位所吸引。刚到这里，乔恩就发现自己和一些杰出的本科生，如詹姆斯·布朗和道格拉斯·富图玛，以及研究生艾伦·布拉什、乔安娜·伯格、肯德尔·科尔宾、赫伯·亨德里克森和尼尔·史密斯交往甚密。乔恩一到那里就找到了查尔斯·西布里，他当时是一位著名的动物学教授。尼尔·史密斯(Neal Smith)在2011年写给凯文·温克(Kevin Winker)的一封电子邮件中描述了他来到西布里实验室的情况:
{"title":"Jon Edward Ahlquist, 1944–2020","authors":"F. Sheldon","doi":"10.1093/auk/ukaa050","DOIUrl":"https://doi.org/10.1093/auk/ukaa050","url":null,"abstract":"Jon Edward Ahlquist died on May 7, 2020, at the age of 75. Thirty years ago, Jon was one of the most famous ornithologists in the world, co-recipient of the 1988 Daniel Giraud Elliot Medal from the National Academy of Sciences and winner of the 1983 Edward’s Prize from the Wilson Ornithological Society. He was also an outstanding bird watcher, artist, and photographer. Yet few ornithologists ever met Jon, let alone knew him as a colleague or friend. He rarely attended American Ornithologists’ Union (AOU) or other scientific meetings, he was not an Elective Member or Fellow of the AOU, and he disappeared from mainstream academia in 1994, only to reemerge in 2017 as a scientific spokesperson for Creationism (https://creation.com/jon-ahlquist). Even for those of us who knew him, Jon was largely an enigma, in many ways open and giving but in others private and almost mysterious. We all realized, however, that Jon was a brilliant intellectual with an encyclopedic knowledge of birds, art, classical music, language, food, photography, and more. He could be hysterically funny, shockingly profane, and outrageous in dress and lifestyle. Although he played a pioneering role in the development of molecular systematics, no one outside a small circle of colleagues knew what he actually did because he never promoted himself publicly and was completely overshadowed and dominated by his mentor and partner of 28 years, Charles G. Sibley. Jon was born on July 27, 1944, the only child of Lula and Arvid Ahlquist. He was raised speaking Finnish in Ashtabula, Ohio, on the edge of Lake Erie, where he developed his bird watching and artistic skills. He had a major showing of his paintings at age 14 and published his first paper (a breeding bird census) at 16. At Ashtabula High School Jon was president of the National Honor Society, editor of the school newspaper, art editor for the yearbook, and valedictorian. Upon graduation, in 1962, he headed to Cornell, drawn not only to its ornithology program but also by Cornell’s historic role in American bird art. Upon arrival, Jon found himself rubbing elbows with such illustrious undergraduates as James Brown and Douglas Futuyma, and postgrads Alan Brush, Joanna Burger, Kendall Corbin, Herb Hendrickson, and Neal Smith. As soon as he arrived, Jon sought out Charles Sibley, who was at that time a renowned professor of zoology. His arrival in Sibley’s lab was described in a 2011 email from Neal Smith to Kevin Winker:","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130370391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT Brood parasitism results in substantial costs to hosts, yet not all species eject foreign eggs. Because the costs of mistakenly ejecting one's own eggs are high, selection may favor ejection behavior only if it is unlikely a host will incorrectly eject her own eggs. Eastern Bluebirds (Sialia sialis) are currently subject to relatively low levels of interspecific brood parasitism but still sometimes eject parasitic eggs. Therefore, we tested which visual cues they use to eject foreign eggs with the prediction that only the most dissimilar eggs would be ejected, reducing the likelihood of a female making a mistake. House Sparrows (Passer domesticus), which occasionally parasitize bluebirds, lay eggs that have an off-white ground color with brown speckling. Therefore, to test which colors or patterns allow for discrimination of parasitic eggs, we generated 3-dimensional (3D)-printed model House Sparrow eggs and painted them entirely off-white, entirely brown, half off-white and half brown, or off-white with brown speckling. We then sequentially placed these 4 different model eggs in the nests of Eastern Bluebirds, with each nest receiving all treatments over the course of 4 days. After watching females enter and leave the nest box just one time after placement of the model egg, we found that speckled eggs were ejected half the time (7 of 14 nests), while no other treatment was ejected more than 3 times. Thus, Eastern Bluebird females eject eggs based primarily on color patterning (i.e. a speckled pattern) rather than coloration per se, and that they can do so quickly, as the average female had removed the model egg within 6 min of entering the nest. Because Eastern Bluebirds do not lay speckled eggs, but some brood parasites do (e.g., House Sparrows, Brown-headed Cowbirds [Molothrus ater]), selection may specifically favor ejection of eggs with a speckled pattern, not just eggs that have within-egg color contrasts. Lay Summary Some birds (brood parasites) lay their eggs in another bird's (host's) nest; if the parasite is successful, the host ends up doing a lot of extra work raising the parasite's young. We painted model eggs to test how Eastern Bluebirds (Sialia sialis), which lay blue eggs, figure out which eggs are theirs and which ones were laid by brood parasites. Eastern Bluebirds rarely get rid of white, brown, or half-white/half-brown model eggs. However, they frequently eject model eggs that are white with brown spots; thus it is the spotting—and not the colors—that indicates to Eastern Bluebirds which eggs are not theirs.
{"title":"Eastern Bluebirds (Sialia sialis) use color patterning, but not the colors themselves, as a cue to eject interspecific parasitic eggs","authors":"M. W. Butler, Maya E Stine, Kwanho C. Kia","doi":"10.1093/auk/ukaa047","DOIUrl":"https://doi.org/10.1093/auk/ukaa047","url":null,"abstract":"ABSTRACT Brood parasitism results in substantial costs to hosts, yet not all species eject foreign eggs. Because the costs of mistakenly ejecting one's own eggs are high, selection may favor ejection behavior only if it is unlikely a host will incorrectly eject her own eggs. Eastern Bluebirds (Sialia sialis) are currently subject to relatively low levels of interspecific brood parasitism but still sometimes eject parasitic eggs. Therefore, we tested which visual cues they use to eject foreign eggs with the prediction that only the most dissimilar eggs would be ejected, reducing the likelihood of a female making a mistake. House Sparrows (Passer domesticus), which occasionally parasitize bluebirds, lay eggs that have an off-white ground color with brown speckling. Therefore, to test which colors or patterns allow for discrimination of parasitic eggs, we generated 3-dimensional (3D)-printed model House Sparrow eggs and painted them entirely off-white, entirely brown, half off-white and half brown, or off-white with brown speckling. We then sequentially placed these 4 different model eggs in the nests of Eastern Bluebirds, with each nest receiving all treatments over the course of 4 days. After watching females enter and leave the nest box just one time after placement of the model egg, we found that speckled eggs were ejected half the time (7 of 14 nests), while no other treatment was ejected more than 3 times. Thus, Eastern Bluebird females eject eggs based primarily on color patterning (i.e. a speckled pattern) rather than coloration per se, and that they can do so quickly, as the average female had removed the model egg within 6 min of entering the nest. Because Eastern Bluebirds do not lay speckled eggs, but some brood parasites do (e.g., House Sparrows, Brown-headed Cowbirds [Molothrus ater]), selection may specifically favor ejection of eggs with a speckled pattern, not just eggs that have within-egg color contrasts. Lay Summary Some birds (brood parasites) lay their eggs in another bird's (host's) nest; if the parasite is successful, the host ends up doing a lot of extra work raising the parasite's young. We painted model eggs to test how Eastern Bluebirds (Sialia sialis), which lay blue eggs, figure out which eggs are theirs and which ones were laid by brood parasites. Eastern Bluebirds rarely get rid of white, brown, or half-white/half-brown model eggs. However, they frequently eject model eggs that are white with brown spots; thus it is the spotting—and not the colors—that indicates to Eastern Bluebirds which eggs are not theirs.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121474986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Walsh, Shawn M. Billerman, Vanya G. Rohwer, Bronwyn G. Butcher, I. Lovette
ABSTRACT Hybrid zones are powerful natural settings for investigating how birds diversify into distinct species. Here we present the first genomic-scale exploration of the Baltimore (Icterus galbula) and Bullock's (I. bullockii) oriole hybrid zone, which is notable for its long history of study and for its prominence in debates about avian species concepts and species limits. We used a reduced-representation sequencing approach to generate a panel of 3,067 genetic markers for 297 orioles sampled along the Platte River, a natural west-to-east transect across the hybrid zone. We then explored patterns of hybridization and introgression by comparing variation in genomic and plumage traits. We found that hybridization remains prevalent in this area, with nearly all orioles within the hybrid zone showing some degree of genomic mixing, and 41% assigned as recent-generation (F1/F2) hybrids. The center and width of the genomic and plumage gradients are concordant and coincident, supporting our finding that classically scored plumage traits are an accurate predictor of pure vs. hybrid genotypes. We find additional support for previous suggestions that the center of this hybrid zone has moved westward since it was first intensively sampled in the 1950s, but that this westward movement had slowed or ceased by the 1970s. Considered in concert, these results support previous inferences that some form of ongoing selection is counteracting the potential homogenization of these orioles via hybridization, thereby supporting their continued taxonomic separation as distinct species. LAY SUMMARY Hybridization between Baltimore and Bullock's Orioles has long captivated biologists and birders alike. Along the river valleys that cross the Great Plains, hybridization is common, leading to debates about whether these are really 2 different oriole species. We sequenced thousands of locations in the oriole genome to discover how much invisible genetic mixing is occurring in this area. Where the species' ranges overlap, many orioles are indeed hybrids, and their combination of plumage traits is a good predictor of their genetic ancestry. Yet the zone of hybridization remains narrow, suggesting that hybridization is a bit of a dead end, and adding to the evidence that these orioles are not blending together into a single species.
{"title":"Genomic and plumage variation across the controversial Baltimore and Bullock's oriole hybrid zone","authors":"J. Walsh, Shawn M. Billerman, Vanya G. Rohwer, Bronwyn G. Butcher, I. Lovette","doi":"10.1093/auk/ukaa044","DOIUrl":"https://doi.org/10.1093/auk/ukaa044","url":null,"abstract":"ABSTRACT Hybrid zones are powerful natural settings for investigating how birds diversify into distinct species. Here we present the first genomic-scale exploration of the Baltimore (Icterus galbula) and Bullock's (I. bullockii) oriole hybrid zone, which is notable for its long history of study and for its prominence in debates about avian species concepts and species limits. We used a reduced-representation sequencing approach to generate a panel of 3,067 genetic markers for 297 orioles sampled along the Platte River, a natural west-to-east transect across the hybrid zone. We then explored patterns of hybridization and introgression by comparing variation in genomic and plumage traits. We found that hybridization remains prevalent in this area, with nearly all orioles within the hybrid zone showing some degree of genomic mixing, and 41% assigned as recent-generation (F1/F2) hybrids. The center and width of the genomic and plumage gradients are concordant and coincident, supporting our finding that classically scored plumage traits are an accurate predictor of pure vs. hybrid genotypes. We find additional support for previous suggestions that the center of this hybrid zone has moved westward since it was first intensively sampled in the 1950s, but that this westward movement had slowed or ceased by the 1970s. Considered in concert, these results support previous inferences that some form of ongoing selection is counteracting the potential homogenization of these orioles via hybridization, thereby supporting their continued taxonomic separation as distinct species. LAY SUMMARY Hybridization between Baltimore and Bullock's Orioles has long captivated biologists and birders alike. Along the river valleys that cross the Great Plains, hybridization is common, leading to debates about whether these are really 2 different oriole species. We sequenced thousands of locations in the oriole genome to discover how much invisible genetic mixing is occurring in this area. Where the species' ranges overlap, many orioles are indeed hybrids, and their combination of plumage traits is a good predictor of their genetic ancestry. Yet the zone of hybridization remains narrow, suggesting that hybridization is a bit of a dead end, and adding to the evidence that these orioles are not blending together into a single species.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132882835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Jahn, V. Cueto, C. S. Fontana, A. Guaraldo, D. Levey, P. Marra, T. Ryder
ABSTRACT Although the migration ecology of birds breeding in the Neotropics is still poorly studied relative to that of their counterparts breeding at north-temperate latitudes, studies conducted over the last 2 decades have revealed that migration in the Neotropics is much more common and diverse than previously thought. These studies have identified dozens of species that migrate latitudinally within South America, altitudinally within various mountain ranges, to and between Caribbean islands, and longitudinally across diverse ecosystems such as the Amazon rainforest. Advances in miniaturized tracking technologies, enormous citizen science databases, and powerful analytical approaches provide an unprecedented ability to detect and evaluate temporally and spatially fine-scale patterns, greatly facilitating the study of migratory patterns across tropical regions. We argue that a renewed effort in research on short- and long-distance bird migration within the Neotropics will allow (1) comparative studies that identify the emergent properties of migratory behavior, (2) identification of the convergent or unique mechanistic drivers of migration across diverse ecological settings, (3) formulation of effective conservation and management plans for migratory Neotropical birds, and (4) predictions about how migratory birds will respond to large-scale climatic changes within the Neotropics. Here, we review the current state of knowledge on Neotropical bird migration, with a focus on South America. We specifically examine similarities and differences in the observed migratory patterns of birds that breed in the Nearctic compared to the Neotropics and highlight key future research questions.
{"title":"Bird migration within the Neotropics","authors":"A. Jahn, V. Cueto, C. S. Fontana, A. Guaraldo, D. Levey, P. Marra, T. Ryder","doi":"10.1093/auk/ukaa033","DOIUrl":"https://doi.org/10.1093/auk/ukaa033","url":null,"abstract":"ABSTRACT Although the migration ecology of birds breeding in the Neotropics is still poorly studied relative to that of their counterparts breeding at north-temperate latitudes, studies conducted over the last 2 decades have revealed that migration in the Neotropics is much more common and diverse than previously thought. These studies have identified dozens of species that migrate latitudinally within South America, altitudinally within various mountain ranges, to and between Caribbean islands, and longitudinally across diverse ecosystems such as the Amazon rainforest. Advances in miniaturized tracking technologies, enormous citizen science databases, and powerful analytical approaches provide an unprecedented ability to detect and evaluate temporally and spatially fine-scale patterns, greatly facilitating the study of migratory patterns across tropical regions. We argue that a renewed effort in research on short- and long-distance bird migration within the Neotropics will allow (1) comparative studies that identify the emergent properties of migratory behavior, (2) identification of the convergent or unique mechanistic drivers of migration across diverse ecological settings, (3) formulation of effective conservation and management plans for migratory Neotropical birds, and (4) predictions about how migratory birds will respond to large-scale climatic changes within the Neotropics. Here, we review the current state of knowledge on Neotropical bird migration, with a focus on South America. We specifically examine similarities and differences in the observed migratory patterns of birds that breed in the Nearctic compared to the Neotropics and highlight key future research questions.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125708535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：