Dana J. Bove, Holly A. Anderson, Matthew A. Smith, Theo A. Kuhn
To better understand the population of the Bald Eagle (Haliaeetus leucocephalus) nesting along northern Colorado’s Front Range, from 2016 to 2022 we studied 86 occupied nests within an area of 20,586 km2. From 2017 to 2020, 279 juveniles fledged from 237 nesting attempts in a smaller, main nest-study area with 68 nests. The nests’ success over these four years ranged from 52 to 70%, and their productivity varied from 1.1 to 1.3. The average nearest-nest distances for three discrete areas in the Front Range (5.03 to 7.26 km) are at least 2.8 to 4.0 times greater than these distances in four nesting populations in wetter regions but shorter than distances observed between nests in drier Arizona. In our study area the coverage of buildings within 400 m of Bald Eagle nests is relatively low by comparison to the coverage around randomly selected points, averaging 1344 m2; for 63% of the nests this coverage was less than 800 m2. We classified the 86 nest territories into eight categories that describe the dominant resource habitat and predicts the eagles’ reliance on Black-tailed Prairie Dogs (Cynomys ludovicianus) versus fish as prey. Predation on fish was predicted to be dominant at 51% (n = 44) of the nests, predation on prairie dogs at 32% (n = 28).
{"title":"Nesting Bald Eagle Population Numbers, Density, Territorial Resources, and Relationship to Human Development in Northern Colorado’s Front Range","authors":"Dana J. Bove, Holly A. Anderson, Matthew A. Smith, Theo A. Kuhn","doi":"10.21199/wb55.1.1","DOIUrl":"https://doi.org/10.21199/wb55.1.1","url":null,"abstract":"To better understand the population of the Bald Eagle (Haliaeetus leucocephalus) nesting along northern Colorado’s Front Range, from 2016 to 2022 we studied 86 occupied nests within an area of 20,586 km2. From 2017 to 2020, 279 juveniles fledged from 237 nesting attempts in a smaller, main nest-study area with 68 nests. The nests’ success over these four years ranged from 52 to 70%, and their productivity varied from 1.1 to 1.3. The average nearest-nest distances for three discrete areas in the Front Range (5.03 to 7.26 km) are at least 2.8 to 4.0 times greater than these distances in four nesting populations in wetter regions but shorter than distances observed between nests in drier Arizona. In our study area the coverage of buildings within 400 m of Bald Eagle nests is relatively low by comparison to the coverage around randomly selected points, averaging 1344 m2; for 63% of the nests this coverage was less than 800 m2. We classified the 86 nest territories into eight categories that describe the dominant resource habitat and predicts the eagles’ reliance on Black-tailed Prairie Dogs (Cynomys ludovicianus) versus fish as prey. Predation on fish was predicted to be dominant at 51% (n = 44) of the nests, predation on prairie dogs at 32% (n = 28).","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140240402","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}
D. Desante, Richard A. Erickson, Gerardo Marrón, Peter Pyle
In preparation for his doctoral studies at Stanford University, the late David F. DeSante spent the fall of 1968 studying migratory landbirds at Cabo San Lucas. Although his hopes to capture numerous vagrant warblers were not met, he amassed an impressive list of distributional records for the Baja California Peninsula at a time when few ornithologists were working there. Among these were peninsular firsts for the Ring-necked Duck (Aythya collaris), Broad-billed Hummingbird (Cynanthus latirostris), Broad-winged Hawk (Buteo platypterus), Bobolink (Dolichonyx oryzivorus), and Painted Bunting (Passerina ciris). Another six species, and one subspecies, were found for the first time in Baja California Sur. Venturing away from the immediate confines of Cabo San Lucas, DeSante established the first peninsular record of the Gray-headed Junco (Junco hyemalis caniceps) and first state records for another five species and one subspecies. Although many of these records have been reported previously, the junior authors believe it is appropriate to synthesize them more completely with current context, in Dave’s honor.
为了准备在斯坦福大学攻读博士学位，已故的大卫-F-迪桑特（David F. DeSante）于 1968 年秋天在卡波圣卢卡斯（Cabo San Lucas）研究迁徙陆鸟。虽然他没能如愿捕捉到大量的流浪莺，但他为下加利福尼亚半岛积累了一份令人印象深刻的分布记录清单，当时在那里工作的鸟类学家寥寥无几。其中包括环颈鸭（Aythya collaris）、宽嘴蜂鸟（Cynanthus latirostris）、宽翅鹰（Buteo platypterus）、山雀（Dolichonyx oryzivorus）和彩鹀（Passerina ciris）的半岛首次记录。另外六个物种和一个亚种也是首次在南下加利福尼亚发现。在远离卡波圣卢卡斯的地方，迪桑特首次发现了半岛灰头鹀（Junco hyemalis caniceps），并首次发现了另外五个物种和一个亚种。虽然这些记录中的很多以前都有报道，但小作者们认为，为了纪念戴夫，应该根据当前的背景对这些记录进行更全面的综合。
{"title":"David F. DeSante’s Birds of Cabo San Lucas, Fall 1968: A Historic Account","authors":"D. Desante, Richard A. Erickson, Gerardo Marrón, Peter Pyle","doi":"10.21199/wb55.1.2","DOIUrl":"https://doi.org/10.21199/wb55.1.2","url":null,"abstract":"In preparation for his doctoral studies at Stanford University, the late David F. DeSante spent the fall of 1968 studying migratory landbirds at Cabo San Lucas. Although his hopes to capture numerous vagrant warblers were not met, he amassed an impressive list of distributional records for the Baja California Peninsula at a time when few ornithologists were working there. Among these were peninsular firsts for the Ring-necked Duck (Aythya collaris), Broad-billed Hummingbird (Cynanthus latirostris), Broad-winged Hawk (Buteo platypterus), Bobolink (Dolichonyx oryzivorus), and Painted Bunting (Passerina ciris). Another six species, and one subspecies, were found for the first time in Baja California Sur. Venturing away from the immediate confines of Cabo San Lucas, DeSante established the first peninsular record of the Gray-headed Junco (Junco hyemalis caniceps) and first state records for another five species and one subspecies. Although many of these records have been reported previously, the junior authors believe it is appropriate to synthesize them more completely with current context, in Dave’s honor.","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140237526","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}
Over 99% of Tricolored Blackbirds (Agelaius tricolor) occur in California. However, small populations persist in Oregon, Washington, Nevada, and Baja California. Loss of wetlands that historically served as foraging and breeding habitat has led to their increasing use of agricultural landscapes including silage fields and cattle feedlots. Here we provide the first documentation of the Tricolored Blackbird in Idaho (26 March–13 May and 3 November–16 December 2023), of up to 30 birds observed at five different locations associated with cattle feedlots, each 10–15 km apart, in Payette and Gem counties. Seven observations included recordings of vocalizations (3-23 April and 14 December 2023), largely coinciding with the final observations at each location, presumably before dispersal to breeding grounds. We consider three hypotheses to explain the apparently sudden occurrence of these birds, including their return to some of the same sites in November 2023: (1) a continued pattern of range expansion due to climate change; (2) an undetected long-term population due to low survey effort; or (3) a large-scale movement in response to flooding and extreme weather in the traditional range. We encourage continued monitoring and surveying of these locations in the coming years and surveying for both new wintering locations and for evidence of the Tricolored Blackbird breeding in Idaho.
{"title":"First Record of Tricolored Blackbirds in Idaho","authors":"Peter J. Olsoy, Katie J. Sorenson","doi":"10.21199/wb55.1.3","DOIUrl":"https://doi.org/10.21199/wb55.1.3","url":null,"abstract":"Over 99% of Tricolored Blackbirds (Agelaius tricolor) occur in California. However, small populations persist in Oregon, Washington, Nevada, and Baja California. Loss of wetlands that historically served as foraging and breeding habitat has led to their increasing use of agricultural landscapes including silage fields and cattle feedlots. Here we provide the first documentation of the Tricolored Blackbird in Idaho (26 March–13 May and 3 November–16 December 2023), of up to 30 birds observed at five different locations associated with cattle feedlots, each 10–15 km apart, in Payette and Gem counties. Seven observations included recordings of vocalizations (3-23 April and 14 December 2023), largely coinciding with the final observations at each location, presumably before dispersal to breeding grounds. We consider three hypotheses to explain the apparently sudden occurrence of these birds, including their return to some of the same sites in November 2023: (1) a continued pattern of range expansion due to climate change; (2) an undetected long-term population due to low survey effort; or (3) a large-scale movement in response to flooding and extreme weather in the traditional range. We encourage continued monitoring and surveying of these locations in the coming years and surveying for both new wintering locations and for evidence of the Tricolored Blackbird breeding in Idaho.","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140237632","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}
here have been many observations of corvids placing a hard-shelled food item onto a roadway, then consuming the food exposed when a passing automobile crushes the shell. However, it has been debated whether corvids perform this behavior intentionally. Our observation of an American Crow (Corvus brachyrhynchos) placing a bivalve on a road, then eating the meat exposed when the shell was run over, supports the idea that corvids intentionally use cars to crack shelled foods.
{"title":"American Crow Cracks Open Bivalve via Automobile","authors":"Sierra R. Glassman, Emily Y. Banno","doi":"10.21199/wb55.1.6","DOIUrl":"https://doi.org/10.21199/wb55.1.6","url":null,"abstract":"here have been many observations of corvids placing a hard-shelled food item onto a roadway, then consuming the food exposed when a passing automobile crushes the shell. However, it has been debated whether corvids perform this behavior intentionally. Our observation of an American Crow (Corvus brachyrhynchos) placing a bivalve on a road, then eating the meat exposed when the shell was run over, supports the idea that corvids intentionally use cars to crack shelled foods.","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140239014","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 second-cycle Black-headed Gull (Chroicocephalus ridibundus), a rare to casual visitor in western North America, remained at Anchorage, Alaska, from 16 July through 17 September 2023, providing a unique opportunity to track and document most stages of its second prebasic molt into definitive (adult) basic plumage. I estimated that the Anchorage bird required approximately 3 to 3.5 months (early/mid-June through late September) to complete the molt of its primaries. This is notably longer than the “average” 2.5 months stated for second-cycle Black-headed Gulls in several publications, but consistent with the duration and calendar limits reported by others for the entire species (mid-May/June through September). The start and duration of rectrix molt relative to the stage of primary molt closely matched that described for gulls in general, and specifically for predefinitive Bonaparte’s (C. philadephia) and Western (Larus occidentalis) gulls. When first observed in mid-July, the Anchorage bird had a white tail, as in definitive plumage, a trait infrequent in first-cycle Black-headed Gulls; then it molted the tail again through August. Although Black-headed Gulls occurring in western North America have been presumed to originate from eastern Asia, the timing of the Anchorage bird’s primary molt closely matched that published for second-cycle Black-headed Gulls in Europe, which has reported to be earlier—though molt schedules of Charadriiformes at the population level are highly variable.
{"title":"Second Prebasic Molt of a Black-headed Gull at Anchorage, Alaska","authors":"Robert L. Scher","doi":"10.21199/wb55.1.5","DOIUrl":"https://doi.org/10.21199/wb55.1.5","url":null,"abstract":"A second-cycle Black-headed Gull (Chroicocephalus ridibundus), a rare to casual visitor in western North America, remained at Anchorage, Alaska, from 16 July through 17 September 2023, providing a unique opportunity to track and document most stages of its second prebasic molt into definitive (adult) basic plumage. I estimated that the Anchorage bird required approximately 3 to 3.5 months (early/mid-June through late September) to complete the molt of its primaries. This is notably longer than the “average” 2.5 months stated for second-cycle Black-headed Gulls in several publications, but consistent with the duration and calendar limits reported by others for the entire species (mid-May/June through September). The start and duration of rectrix molt relative to the stage of primary molt closely matched that described for gulls in general, and specifically for predefinitive Bonaparte’s (C. philadephia) and Western (Larus occidentalis) gulls. When first observed in mid-July, the Anchorage bird had a white tail, as in definitive plumage, a trait infrequent in first-cycle Black-headed Gulls; then it molted the tail again through August. Although Black-headed Gulls occurring in western North America have been presumed to originate from eastern Asia, the timing of the Anchorage bird’s primary molt closely matched that published for second-cycle Black-headed Gulls in Europe, which has reported to be earlier—though molt schedules of Charadriiformes at the population level are highly variable.","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140240045","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}
We estimated survival of Black-chinned Hummingbird (Archilochus alexandri) nests in southwest Colorado in 1998, 2001, and 2004 by means of models generated in program Mark. The best supported, and parsimonious, model suggested nest age (i.e., time since the nest was initiated) as the most important variable in indicating nest survival; daily survival rates of nests with eggs were lower than those of nests with nestlings. Substrate type was a second covariate that had some support in describing nest survival. Nests in Gambel oak (Quercus gambelii) or narrow-leaf cottonwood (Populus angustifolia) had greater daily survival rates than did those built in other substrates. No other ecological covariates were strongly supported in explaining nest survival. Of the 24 nests studied, 10 were successful, fledging an average of 1.7 (standard error 0.14) chicks.
{"title":"Factors Influencing Survival of Black-chinned Hummingbird Nests in Southwest Colorado","authors":"J. C. Ortega, C. P. Ortega","doi":"10.21199/wb55.1.4","DOIUrl":"https://doi.org/10.21199/wb55.1.4","url":null,"abstract":"We estimated survival of Black-chinned Hummingbird (Archilochus alexandri) nests in southwest Colorado in 1998, 2001, and 2004 by means of models generated in program Mark. The best supported, and parsimonious, model suggested nest age (i.e., time since the nest was initiated) as the most important variable in indicating nest survival; daily survival rates of nests with eggs were lower than those of nests with nestlings. Substrate type was a second covariate that had some support in describing nest survival. Nests in Gambel oak (Quercus gambelii) or narrow-leaf cottonwood (Populus angustifolia) had greater daily survival rates than did those built in other substrates. No other ecological covariates were strongly supported in explaining nest survival. Of the 24 nests studied, 10 were successful, fledging an average of 1.7 (standard error 0.14) chicks.","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140240465","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}
Although the ornithological history of southern Brazil has been amassed over the last 200 years, few attempts have been made to describe how species have accumulated. Furthermore, the collaboration of citizen scientists has considerably changed the way researchers analyze empirical data. Caprimulgidae (Nightjars and Nighthawks) species were used to illustrate how species have been recorded since the 1800s in Paraná State by comparing traditional and citizen science data. In addition, reports from both researchers and citizen scientists on the breeding biology of these caprimulgids have been verified. A literature review was conducted searching for the Caprimulgid species within the territory of Paraná. Regarding citizen science, records were obtained from four ornithological platforms. Overall, 14 species were detected within the state, 13 of which have been described in the literature, including 1 endemic to the Atlantic Forest and 3 threatened species. Citizen scientists detected all 13 taxa, in addition to one undocumented species that has never been recorded by researchers. There were 12 times more records on ornithological platforms in half of the sampling effort accumulated in studies, but most of them date from the last five years. Citizen scientists also visited 4.5 times more locations than researchers. Citizen scientists accumulated more records around September and November, and most (59%) records were from 2020–2022. Researchers mentioned species as early as 1820, while continuous studies only began during the 1980s; they concentrated their fieldwork mostly in September. Only one (2%) study sought to describe the breeding biology of a caprimulgid species, but there were 84 observations on ornithological platforms between 2004–2022 on their reproduction. Because of the evident mismatch between traditional and citizen science data due to a lack of congruence between their actions, it is suggested that ornithology in Paraná, as well as other Brazilian regions, would benefit the most if traditional and citizen scientists improved their networking communication to focus on common purposes instead of acting independently.
{"title":"200 Years of Caprimulgid Records in Southern Brazil: A Comparison between the Literature and Citizen Science Data","authors":"Vagner Cavarzere","doi":"10.3390/birds4040026","DOIUrl":"https://doi.org/10.3390/birds4040026","url":null,"abstract":"Although the ornithological history of southern Brazil has been amassed over the last 200 years, few attempts have been made to describe how species have accumulated. Furthermore, the collaboration of citizen scientists has considerably changed the way researchers analyze empirical data. Caprimulgidae (Nightjars and Nighthawks) species were used to illustrate how species have been recorded since the 1800s in Paraná State by comparing traditional and citizen science data. In addition, reports from both researchers and citizen scientists on the breeding biology of these caprimulgids have been verified. A literature review was conducted searching for the Caprimulgid species within the territory of Paraná. Regarding citizen science, records were obtained from four ornithological platforms. Overall, 14 species were detected within the state, 13 of which have been described in the literature, including 1 endemic to the Atlantic Forest and 3 threatened species. Citizen scientists detected all 13 taxa, in addition to one undocumented species that has never been recorded by researchers. There were 12 times more records on ornithological platforms in half of the sampling effort accumulated in studies, but most of them date from the last five years. Citizen scientists also visited 4.5 times more locations than researchers. Citizen scientists accumulated more records around September and November, and most (59%) records were from 2020–2022. Researchers mentioned species as early as 1820, while continuous studies only began during the 1980s; they concentrated their fieldwork mostly in September. Only one (2%) study sought to describe the breeding biology of a caprimulgid species, but there were 84 observations on ornithological platforms between 2004–2022 on their reproduction. Because of the evident mismatch between traditional and citizen science data due to a lack of congruence between their actions, it is suggested that ornithology in Paraná, as well as other Brazilian regions, would benefit the most if traditional and citizen scientists improved their networking communication to focus on common purposes instead of acting independently.","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136104626","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}
Wildlife–aircraft collisions represent a safety and financial challenge, necessitating site-specific hazard assessments, which are generally based on species’ attributes and collision frequencies. However, for many bird species, collision probability and risk may not be distributed equally among individuals, with sex and age differences possible but rarely examined. We examine Australian Magpies, a resident, grassland species of bird in southeastern Australia frequently involved in collisions with aircraft at airports, and which can be sexed (adults) and aged. We compared collision rates recorded at Melbourne Airport, Victoria, Australia, with airside counts of magpies, recording, when observable, the sex and age of the birds. Adult females and males were similarly abundant at the airport (46.6% female), but females were struck relatively more frequently than males (78.1% female). Juvenile (first-year) magpies were struck more frequently than expected based on their representation in bird counts. We show an example of where some demographic groups within species represent higher hazard potential to aircraft than others, and management which manipulates demography of magpies at and near the airport (such as discouraging local breeding and targeted harassment/dispersal) may be fruitful.
{"title":"Sex and Age Bias in Australian Magpies Struck by Aircraft","authors":"William K. Steele, Michael A. Weston","doi":"10.3390/birds4040025","DOIUrl":"https://doi.org/10.3390/birds4040025","url":null,"abstract":"Wildlife–aircraft collisions represent a safety and financial challenge, necessitating site-specific hazard assessments, which are generally based on species’ attributes and collision frequencies. However, for many bird species, collision probability and risk may not be distributed equally among individuals, with sex and age differences possible but rarely examined. We examine Australian Magpies, a resident, grassland species of bird in southeastern Australia frequently involved in collisions with aircraft at airports, and which can be sexed (adults) and aged. We compared collision rates recorded at Melbourne Airport, Victoria, Australia, with airside counts of magpies, recording, when observable, the sex and age of the birds. Adult females and males were similarly abundant at the airport (46.6% female), but females were struck relatively more frequently than males (78.1% female). Juvenile (first-year) magpies were struck more frequently than expected based on their representation in bird counts. We show an example of where some demographic groups within species represent higher hazard potential to aircraft than others, and management which manipulates demography of magpies at and near the airport (such as discouraging local breeding and targeted harassment/dispersal) may be fruitful.","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136234181","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}
Over evolutionary times, the eye has acquired several adaptations to improve feeding efficiency and reduce predation pressure. Eye size, in particular, represents a target for selection, as it affects light capture and image resolution. Previous research on variation in eye size across species has focused on ecological factors related to light availability and foraging needs. Larger eyes are also thought to allow species to detect distant predators more easily, but this conjecture has not been examined across species. I predicted that risk-averse species or those exposed to high predation risk benefit from relatively larger eyes to enhance predator detection. To test the prediction, I performed a comparative analysis involving 660 species of birds while controlling for phylogeny, body size and other known ecological correlates of eye size. The results show that species at the slow end of the life history continuum, which emphasize survival over reproduction and are expected to be risk-averse, have evolved relatively larger eyes. In addition, solitary species, which cannot rely on others in their groups to decrease predation risk, are also characterized by relatively larger eyes. The results indicate that predation risk, through its association with life history and sociality, is an important ecological factor in the evolution of eye size across species.
{"title":"Life History and Sociality Predict Variation in Eye Size across Birds","authors":"G. Beauchamp","doi":"10.3390/birds4030024","DOIUrl":"https://doi.org/10.3390/birds4030024","url":null,"abstract":"Over evolutionary times, the eye has acquired several adaptations to improve feeding efficiency and reduce predation pressure. Eye size, in particular, represents a target for selection, as it affects light capture and image resolution. Previous research on variation in eye size across species has focused on ecological factors related to light availability and foraging needs. Larger eyes are also thought to allow species to detect distant predators more easily, but this conjecture has not been examined across species. I predicted that risk-averse species or those exposed to high predation risk benefit from relatively larger eyes to enhance predator detection. To test the prediction, I performed a comparative analysis involving 660 species of birds while controlling for phylogeny, body size and other known ecological correlates of eye size. The results show that species at the slow end of the life history continuum, which emphasize survival over reproduction and are expected to be risk-averse, have evolved relatively larger eyes. In addition, solitary species, which cannot rely on others in their groups to decrease predation risk, are also characterized by relatively larger eyes. The results indicate that predation risk, through its association with life history and sociality, is an important ecological factor in the evolution of eye size across species.","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87504529","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}
According to current literature, the Kelp Gull (Larus dominicanus) matures at the same rate and molts according to the same patterns as most other large gulls, such as the American Herring (L. argentatus smithsonianus) and Western (L. occidentalis). The Kelp Gull, however, is widespread through the Southern Hemisphere, with separate populations occupying no fewer than four different climate zones and breeding at different times of the year; the molt of some of those populations appears to have not been studied yet. Here we demonstrate that many immature Kelp Gulls of the Peruvian population undergo much more extensive first and second prealternate molts than has been known so far and achieve an adult-like plumage aspect in as soon as 2.5 years rather than the usual 4. In these respects, these Kelp Gulls recall the Yellow-footed Gull (L. livens) or subspecies heuglini and fuscus of the Lesser Black-backed Gull (L. fuscus).
{"title":"Extensive Prealternate Molts in Peruvian Kelp Gulls","authors":"Peter Adriaens, Amar Ayyash, M. Muusse","doi":"10.21199/wb54.3.6","DOIUrl":"https://doi.org/10.21199/wb54.3.6","url":null,"abstract":"According to current literature, the Kelp Gull (Larus dominicanus) matures at the same rate and molts according to the same patterns as most other large gulls, such as the American Herring (L. argentatus smithsonianus) and Western (L. occidentalis). The Kelp Gull, however, is widespread through the Southern Hemisphere, with separate populations occupying no fewer than four different climate zones and breeding at different times of the year; the molt of some of those populations appears to have not been studied yet. Here we demonstrate that many immature Kelp Gulls of the Peruvian population undergo much more extensive first and second prealternate molts than has been known so far and achieve an adult-like plumage aspect in as soon as 2.5 years rather than the usual 4. In these respects, these Kelp Gulls recall the Yellow-footed Gull (L. livens) or subspecies heuglini and fuscus of the Lesser Black-backed Gull (L. fuscus).","PeriodicalId":52426,"journal":{"name":"Western Birds","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79161941","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}
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