In Prairie Falcons (Falco mexicanus), females are considerably larger than males, as in most diurnal birds of prey. This phenomenon, known as reversed sexual dimorphism (RSD), is usually associated with asymmetry in parental care: the smaller male provides most of the food during the nesting season, whereas the larger female incubates the eggs, and broods and protects the young. To evaluate this relationship in Prairie Falcons, we quantitatively assessed parental roles of 52 pairs of Prairie Falcons nesting in southwestern Idaho, over a 4-yr period (1984–1987). We collected behavioral observations for each pair, from the establishment of a nesting territory until young were 30–35 d old (fledging age), for a total of 613 observation days (9089 hr). We found that male and female falcons shared some tasks, although not necessarily equally, including incubation, provisioning prey and nest defense. Females accounted for two-thirds of the diurnal incubation responsibility and males for one-third. Males and females made comparable efforts in food provisioning; similarly, nest defense, here defined as aggressive interactions with (potential) nest predators, did not differ between the sexes. Other behaviors, such as brooding, hunting, and nest attendance were performed more by one sex than the other. Brooding was carried out primarily by females, and they showed consistently higher nest attendance compared to males. Males hunted significantly more than females and delivered most prey items to the nest site. Overall, sex roles exhibited by nesting Prairie Falcons in our study largely agreed with predictions based on RSD.
{"title":"Parental Roles of Nesting Prairie Falcons in Relation to Reversed Sexual Dimorphism","authors":"A. Holthuijzen, Lenora Oosterhuis","doi":"10.3356/jrr-22-78","DOIUrl":"https://doi.org/10.3356/jrr-22-78","url":null,"abstract":"\u0000 In Prairie Falcons (Falco mexicanus), females are considerably larger than males, as in most diurnal birds of prey. This phenomenon, known as reversed sexual dimorphism (RSD), is usually associated with asymmetry in parental care: the smaller male provides most of the food during the nesting season, whereas the larger female incubates the eggs, and broods and protects the young. To evaluate this relationship in Prairie Falcons, we quantitatively assessed parental roles of 52 pairs of Prairie Falcons nesting in southwestern Idaho, over a 4-yr period (1984–1987). We collected behavioral observations for each pair, from the establishment of a nesting territory until young were 30–35 d old (fledging age), for a total of 613 observation days (9089 hr). We found that male and female falcons shared some tasks, although not necessarily equally, including incubation, provisioning prey and nest defense. Females accounted for two-thirds of the diurnal incubation responsibility and males for one-third. Males and females made comparable efforts in food provisioning; similarly, nest defense, here defined as aggressive interactions with (potential) nest predators, did not differ between the sexes. Other behaviors, such as brooding, hunting, and nest attendance were performed more by one sex than the other. Brooding was carried out primarily by females, and they showed consistently higher nest attendance compared to males. Males hunted significantly more than females and delivered most prey items to the nest site. Overall, sex roles exhibited by nesting Prairie Falcons in our study largely agreed with predictions based on RSD.","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139389618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In Israel, Long-eared Owls (Asio otus) were considered primarily a wintering species with documented sporadic breeding. However, by the turn of the last century, it had become an increasingly numerous breeding species in the northern and central parts of the country. Based on the analysis of nest numbers in the Judea region, we determined that the population increased by at least 22% each year between 2003 and 2008, from 28 known nests in 2003 to 118 in 2008. We believe our study was conducted during the initial years for the Long-eared Owl population expansion in the region. We found that birds nesting in more-urban areas produced fewer offspring per brood than birds in more rural areas. We also found that nestlings from more-urban areas, exposed to artificial light at night, fledged earlier than birds from wild areas. The rapid growth in the numbers of nesting Long-eared Owls in the Judea region was likely due, at least in part, to the species’ adaptation to urban areas.
{"title":"Habitat Factors Driving Long-eared Owl (Asio otus) Population Growth and Productivity in the Judea Region","authors":"Ezra Hadad, J. Kosicki, R. Yosef","doi":"10.3356/jrr-22-118","DOIUrl":"https://doi.org/10.3356/jrr-22-118","url":null,"abstract":"\u0000 In Israel, Long-eared Owls (Asio otus) were considered primarily a wintering species with documented sporadic breeding. However, by the turn of the last century, it had become an increasingly numerous breeding species in the northern and central parts of the country. Based on the analysis of nest numbers in the Judea region, we determined that the population increased by at least 22% each year between 2003 and 2008, from 28 known nests in 2003 to 118 in 2008. We believe our study was conducted during the initial years for the Long-eared Owl population expansion in the region. We found that birds nesting in more-urban areas produced fewer offspring per brood than birds in more rural areas. We also found that nestlings from more-urban areas, exposed to artificial light at night, fledged earlier than birds from wild areas. The rapid growth in the numbers of nesting Long-eared Owls in the Judea region was likely due, at least in part, to the species’ adaptation to urban areas.","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A Most Remarkable Creature: The Hidden Life and Epic Journey of the World’s Smartest Birds of Prey","authors":"","doi":"10.3356/jrr24502","DOIUrl":"https://doi.org/10.3356/jrr24502","url":null,"abstract":"","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139452015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Winter Interactions of Sharp-shinned Hawks with Prey","authors":"Paul Hendricks","doi":"10.3356/jrr-23-17","DOIUrl":"https://doi.org/10.3356/jrr-23-17","url":null,"abstract":"","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139388579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tyler J. Michels, Greg Evans, Thomas Kelly, Nicholas Gonzalez, Marcel Bozas, Craig van der Heiden
{"title":"First Detection of Highly Pathogenic Avian Influenza Virus in a Crested Caracara","authors":"Tyler J. Michels, Greg Evans, Thomas Kelly, Nicholas Gonzalez, Marcel Bozas, Craig van der Heiden","doi":"10.3356/jrr-23-00014","DOIUrl":"https://doi.org/10.3356/jrr-23-00014","url":null,"abstract":"","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thomas W. Wittig, Paige E. Howell, Kathleen E. Clark
Constructing nests costs birds time and energy and may influence breeding success and productivity. The precise nature and extent of these costs is understudied, particularly among raptor species. We used linear and generalized linear mixed models to examine the time and reproductive costs of nest construction to Bald Eagles (Haliaeetus leucocephalus) in New Jersey, USA, from 2009 to 2021. To differentiate nest construction costs from the influence of experience, we separately analyzed the breeding performance and phenology of new pairs constructing nests, established pairs constructing nests, and established pairs reusing nests. We also considered the influence of weather, year, and ecoregion. New territorial pairs building nests were generally less successful and productive than established pairs building or reusing nests. However, these trends were largely attributable to a greater egg-laying rate among established pairs. Nest building pairs, new and established, were generally delayed in egg laying, hatching, and nestling fledging compared to established pairs reusing nests; new pairs were notably more delayed than established pairs building nests. Territorial pairs in the Atlantic Coastal Pine Barrens were less successful and productive than pairs in other ecoregions. Higher precipitation around the egg laying period was predictive of lower nest success and productivity rates but did not appear to affect phenology. Higher temperatures around this period also lowered these rates, with the further effect of advancing phenology. In New Jersey, climate change appears to be advancing breeding phenology and could constrain productivity by century’s end, though we anticipate that density dependence will regulate and lower Bald Eagle breeding performance prior to this period. Breeding success and productivity rates, as well as the effects of year in our models, indicate that New Jersey’s breeding Bald Eagle population is still healthy and growing. Overall, our results indicate that nest construction imposes minor temporal costs on Bald Eagles but does not meaningfully affect their breeding success or productivity, which may help inform management of Bald Eagle nests and populations.
{"title":"Nest Construction Costs Bald Eagles Time but not Breeding Success or Productivity","authors":"Thomas W. Wittig, Paige E. Howell, Kathleen E. Clark","doi":"10.3356/jrr-22-112","DOIUrl":"https://doi.org/10.3356/jrr-22-112","url":null,"abstract":"\u0000 Constructing nests costs birds time and energy and may influence breeding success and productivity. The precise nature and extent of these costs is understudied, particularly among raptor species. We used linear and generalized linear mixed models to examine the time and reproductive costs of nest construction to Bald Eagles (Haliaeetus leucocephalus) in New Jersey, USA, from 2009 to 2021. To differentiate nest construction costs from the influence of experience, we separately analyzed the breeding performance and phenology of new pairs constructing nests, established pairs constructing nests, and established pairs reusing nests. We also considered the influence of weather, year, and ecoregion. New territorial pairs building nests were generally less successful and productive than established pairs building or reusing nests. However, these trends were largely attributable to a greater egg-laying rate among established pairs. Nest building pairs, new and established, were generally delayed in egg laying, hatching, and nestling fledging compared to established pairs reusing nests; new pairs were notably more delayed than established pairs building nests. Territorial pairs in the Atlantic Coastal Pine Barrens were less successful and productive than pairs in other ecoregions. Higher precipitation around the egg laying period was predictive of lower nest success and productivity rates but did not appear to affect phenology. Higher temperatures around this period also lowered these rates, with the further effect of advancing phenology. In New Jersey, climate change appears to be advancing breeding phenology and could constrain productivity by century’s end, though we anticipate that density dependence will regulate and lower Bald Eagle breeding performance prior to this period. Breeding success and productivity rates, as well as the effects of year in our models, indicate that New Jersey’s breeding Bald Eagle population is still healthy and growing. Overall, our results indicate that nest construction imposes minor temporal costs on Bald Eagles but does not meaningfully affect their breeding success or productivity, which may help inform management of Bald Eagle nests and populations.","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Robert K. Murphy, B. Millsap, D. Stahlecker, C. Boal, Brian W. Smith, Shea D. Mullican, Corrie C. Borgman
ABSTRACT. Much of the US Southern Great Plains (SGP) continues to undergo intensive energy development that could affect the region's Golden Eagles (Aquila chrysaetos), yet the species' population status there is unknown. During 2011–2020, we used satellite telemetry to assess annual survival rates and causes of mortality among 40 preadult (<3 yr of age) Golden Eagles in the SGP; 29 were monitored beginning at the late nestling stage and 11 immigrated into the SGP from western regions. For comparison we monitored 15 preadult Golden Eagles from nests in the Central Great Plains (CGP), where energy development was less extensive. We estimated survival rates by using a multi-state model in a Bayesian framework that accounted for probabilities of causes of death. Mean annual survival in the SGP during the preadult period was 0.060, versus 0.512 in the CGP and ∼0.7–0.9 reported elsewhere in the coterminous western USA. Mexican chicken bugs (Haematosiphon inodorus) were implicated in deaths of at least seven Golden Eagles during the ∼2-wk late nestling stage and in two deaths <3 mo after fledging. Energy infrastructure especially electrocutions accounted for 12 (57.1%) of 21 deaths of post-fledged preadults. Seven of 11 immigrant eagles died. Overall, probabilities of death of a Golden Eagle during the preadult period in the SGP due to Mexican chicken bugs and to electrocution were both 0.345. We estimated that the SGP population may be declining 9% annually due to poor recruitment; mitigation of underlying factors should be a priority for managing Golden Eagles in the western USA. RESUMEN. Buena parte de las Grandes Llanuras del Sur (GLS) de EEUU continúan sometidas a un desarrollo energético intensivo que podría afectar a los individuos de Aquila chrysaetos de la región; sin embargo, el estado de la población de la especie en esta zona es desconocido. Durante 2011–2020, usamos telemetría satelital para evaluar las tasas de supervivencia anuales y las causas de mortalidad entre 40 águilas preadultas (<3 años de edad) de A. chrysaetos en las GLS; 29 fueron monitoreadas a partir de la etapa tardía de polluelo y 11 inmigraron desde regiones del oeste. Para hacer una comparación, monitoreamos 15 águilas preadultas de A. chrysaetos en nidos de las Grandes Llanuras Centrales (GLC), donde el desarrollo energético era menos extenso. Estimamos las tasas de supervivencia utilizando un modelo multi-estado en un marco de trabajo bayesiano que tuvo en cuenta las probabilidades de las causas de muerte. La supervivencia media anual en las GLS durante el periodo preadulto fue de 0.060, en comparación con 0.512 en las GLC y ∼0.7–0.9 en otras partes del oeste contiguo de EEUU. La chinche Haematosiphon inodorus estuvo implicada en la muerte de al menos siete águilas durante las últimas ∼2 semanas de la etapa tardía de polluelo y en dos muertes durante el inicio del postemplumamiento. La infraestructura energética, especialmente las electrocuciones, representaron 12 (57.
{"title":"Ectoparasitism and Energy Infrastructure Limit Survival of Preadult Golden Eagles in the Southern Great Plains","authors":"Robert K. Murphy, B. Millsap, D. Stahlecker, C. Boal, Brian W. Smith, Shea D. Mullican, Corrie C. Borgman","doi":"10.3356/JRR-21-72","DOIUrl":"https://doi.org/10.3356/JRR-21-72","url":null,"abstract":"ABSTRACT. Much of the US Southern Great Plains (SGP) continues to undergo intensive energy development that could affect the region's Golden Eagles (Aquila chrysaetos), yet the species' population status there is unknown. During 2011–2020, we used satellite telemetry to assess annual survival rates and causes of mortality among 40 preadult (<3 yr of age) Golden Eagles in the SGP; 29 were monitored beginning at the late nestling stage and 11 immigrated into the SGP from western regions. For comparison we monitored 15 preadult Golden Eagles from nests in the Central Great Plains (CGP), where energy development was less extensive. We estimated survival rates by using a multi-state model in a Bayesian framework that accounted for probabilities of causes of death. Mean annual survival in the SGP during the preadult period was 0.060, versus 0.512 in the CGP and ∼0.7–0.9 reported elsewhere in the coterminous western USA. Mexican chicken bugs (Haematosiphon inodorus) were implicated in deaths of at least seven Golden Eagles during the ∼2-wk late nestling stage and in two deaths <3 mo after fledging. Energy infrastructure especially electrocutions accounted for 12 (57.1%) of 21 deaths of post-fledged preadults. Seven of 11 immigrant eagles died. Overall, probabilities of death of a Golden Eagle during the preadult period in the SGP due to Mexican chicken bugs and to electrocution were both 0.345. We estimated that the SGP population may be declining 9% annually due to poor recruitment; mitigation of underlying factors should be a priority for managing Golden Eagles in the western USA. RESUMEN. Buena parte de las Grandes Llanuras del Sur (GLS) de EEUU continúan sometidas a un desarrollo energético intensivo que podría afectar a los individuos de Aquila chrysaetos de la región; sin embargo, el estado de la población de la especie en esta zona es desconocido. Durante 2011–2020, usamos telemetría satelital para evaluar las tasas de supervivencia anuales y las causas de mortalidad entre 40 águilas preadultas (<3 años de edad) de A. chrysaetos en las GLS; 29 fueron monitoreadas a partir de la etapa tardía de polluelo y 11 inmigraron desde regiones del oeste. Para hacer una comparación, monitoreamos 15 águilas preadultas de A. chrysaetos en nidos de las Grandes Llanuras Centrales (GLC), donde el desarrollo energético era menos extenso. Estimamos las tasas de supervivencia utilizando un modelo multi-estado en un marco de trabajo bayesiano que tuvo en cuenta las probabilidades de las causas de muerte. La supervivencia media anual en las GLS durante el periodo preadulto fue de 0.060, en comparación con 0.512 en las GLC y ∼0.7–0.9 en otras partes del oeste contiguo de EEUU. La chinche Haematosiphon inodorus estuvo implicada en la muerte de al menos siete águilas durante las últimas ∼2 semanas de la etapa tardía de polluelo y en dos muertes durante el inicio del postemplumamiento. La infraestructura energética, especialmente las electrocuciones, representaron 12 (57.","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139153173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Breeding Dispersion of Raptors in the Junggar Basin, Xinjiang, China, Including a Case of Close Nesting of Saker Falcons and Golden Eagles","authors":"I. Angelov, R. Maming, Andrew Dixon","doi":"10.3356/JRR-22-00086","DOIUrl":"https://doi.org/10.3356/JRR-22-00086","url":null,"abstract":"","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139153156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mercy Melo, Kirsten Fuller, Sue Robertson, B. Robertson, Laurie J. Goodrich, David King, J. Therrien
ABSTRACT. Urbanization increasingly causes alterations in prey diversity and abundance, land cover, and human disturbance, subsequently impacting populations of even the most adaptable species. American Kestrels are currently considered urban adapters, which may be veiling the influence of urbanization on their continental population decline. We quantified overwintering abundance and sex ratios of American Kestrels throughout the past three decades in a rapidly developing region of the species' wintering range in southeast Florida to study spatial and temporal population trends relative to degree of urbanization. We detected a significant negative correlation between annual building density and kestrel abundance. Sex ratios also significantly shifted from predominantly female to predominantly male over time and in association with increased residential development. This trend suggests that developed landscapes may represent lower quality territories, as females typically occupy better quality overwintering habitat than males. These results suggest that urbanization may negatively impact overwintering American Kestrel populations in this region and should be investigated as a possible factor contributing to the overall continental population decline, particularly in the eastern flyway where urbanization is prevalent. RESUMEN. La urbanización causa cada vez más alteraciones en la diversidad y abundancia de presas, la cobertura del suelo y la perturbación humana, impactando posteriormente en las poblaciones incluso de las especies más adaptables. Falco sparverius es considerada actualmente como una especie adaptada a los ambientes urbanos, lo que podría estar enmascarando la influencia de la urbanización en su declive poblacional continental. Para estudiar las tendencias poblacionales espaciales y temporales en relación con el grado de urbanización, cuantificamos la abundancia invernal y las proporciones de sexos de F. sparverius a lo largo de las últimas tres décadas en una región de rápido desarrollo urbano dentro del área de invernada de la especie en el sureste de Florida. Detectamos una correlación negativa significativa entre la densidad anual de edificios y la abundancia de individuos de F. sparverius. Con el tiempo, la proporción de sexos también cambió significativamente, desde un predominio de hembras a un predominio de machos, en relación con un mayor desarrollo residencial. Esta tendencia sugiere que los paisajes urbanizados pueden representar territorios de menor calidad, ya que las hembras suelen ocupar hábitats de invernada de mejor calidad que los machos. Estos resultados sugieren que la urbanización podría afectar negativamente a las poblaciones invernantes de F. sparverius en esta región y se debería investigar como un posible factor que contribuye al declive poblacional continental general, especialmente en la ruta migratoria oriental donde la urbanización es prevalente. [Traducción del equipo editorial]
{"title":"Rapid Urbanization Alters Overwintering Abundance and Sex Ratio of the American Kestrel","authors":"Mercy Melo, Kirsten Fuller, Sue Robertson, B. Robertson, Laurie J. Goodrich, David King, J. Therrien","doi":"10.3356/JRR-22-00107","DOIUrl":"https://doi.org/10.3356/JRR-22-00107","url":null,"abstract":"ABSTRACT. Urbanization increasingly causes alterations in prey diversity and abundance, land cover, and human disturbance, subsequently impacting populations of even the most adaptable species. American Kestrels are currently considered urban adapters, which may be veiling the influence of urbanization on their continental population decline. We quantified overwintering abundance and sex ratios of American Kestrels throughout the past three decades in a rapidly developing region of the species' wintering range in southeast Florida to study spatial and temporal population trends relative to degree of urbanization. We detected a significant negative correlation between annual building density and kestrel abundance. Sex ratios also significantly shifted from predominantly female to predominantly male over time and in association with increased residential development. This trend suggests that developed landscapes may represent lower quality territories, as females typically occupy better quality overwintering habitat than males. These results suggest that urbanization may negatively impact overwintering American Kestrel populations in this region and should be investigated as a possible factor contributing to the overall continental population decline, particularly in the eastern flyway where urbanization is prevalent. RESUMEN. La urbanización causa cada vez más alteraciones en la diversidad y abundancia de presas, la cobertura del suelo y la perturbación humana, impactando posteriormente en las poblaciones incluso de las especies más adaptables. Falco sparverius es considerada actualmente como una especie adaptada a los ambientes urbanos, lo que podría estar enmascarando la influencia de la urbanización en su declive poblacional continental. Para estudiar las tendencias poblacionales espaciales y temporales en relación con el grado de urbanización, cuantificamos la abundancia invernal y las proporciones de sexos de F. sparverius a lo largo de las últimas tres décadas en una región de rápido desarrollo urbano dentro del área de invernada de la especie en el sureste de Florida. Detectamos una correlación negativa significativa entre la densidad anual de edificios y la abundancia de individuos de F. sparverius. Con el tiempo, la proporción de sexos también cambió significativamente, desde un predominio de hembras a un predominio de machos, en relación con un mayor desarrollo residencial. Esta tendencia sugiere que los paisajes urbanizados pueden representar territorios de menor calidad, ya que las hembras suelen ocupar hábitats de invernada de mejor calidad que los machos. Estos resultados sugieren que la urbanización podría afectar negativamente a las poblaciones invernantes de F. sparverius en esta región y se debería investigar como un posible factor que contribuye al declive poblacional continental general, especialmente en la ruta migratoria oriental donde la urbanización es prevalente. [Traducción del equipo editorial]","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139154351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jared Zimmerman, Janell M. Brush, Meaghan N. Evans, Kristin Rogers, Stephen A. Nesbitt, Erin Leone, W. A. Cox, Michelle van Deventer, Craig A. Faulhaber
ABSTRACT. The range-wide recovery of Bald Eagles (Haliaeetus leucocephalus) is one of the great North American conservation successes, with the Bald Eagle population in Florida contributing substantially to this recovery. Florida has one of the densest concentrations of nesting Bald Eagles in the lower 48 states and sustained a population monitoring program that spanned 45 yr. We used nest monitoring data from 1972–2017 to quantify changes in the size, extent, and productivity of the breeding Bald Eagle population in Florida. We documented an increase in the number of occupied Bald Eagle territories from 88 in 1973 to an estimated 1565 in 2017, with nests recorded in 64 of Florida's 67 counties by the end of the monitoring efforts. Mean annual growth rate in the number of occupied eagle territories in Florida was 5.5 ± 1.1% (SE). High reproductive rates, exemplified by a mean productivity of 1.13 ± 0.02 fledglings per occupied nest, a mean brood size of 1.54 ± 0.01 fledglings per successful nest, and the production of nearly 40,000 fledglings over a 45-yr period, translated into substantial gains for the state and southeastern US Bald Eagle population. Eagles have established a large, spatially expansive, and productive breeding population in Florida, one that exceeded the conservation objectives established when the species was state-delisted in 2008. These data provided key insights into the breeding ecology, recovery, and long-term stability of Bald Eagles in Florida. Given the predicted increase in the human population and landscape modification anticipated in the coming years, the conservation of the eagle population within Florida will require adaptive management strategies.
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