Journal of Raptor Research最新文献

{"title":"Sibling Aggression, Feeding Rates, and Hatch Rank of Nestling Red-Shouldered Hawks (Buteo lineatus)","authors":"Sara J. Miller, C. Dykstra, Virginie Rolland, Melinda M. Simon, Jeffrey L. Hays, J. Bednarz","doi":"10.3356/JRR-22-76","DOIUrl":"https://doi.org/10.3356/JRR-22-76","url":null,"abstract":"ABSTRACT. In many raptor species, hatching asynchrony results in a size hierarchy among nestlings, which may facilitate brood reduction by means of sibling aggression-induced mortality, especially in times of low food resources. However, few researchers have investigated the relationships among hatching asynchrony, sibling aggression, and nestling feeding rates in raptors. We studied the influence of hatch rank, brood size, and brood age on aggression and feeding rates among Red-shouldered Hawk (Buteo lineatus) nestlings in suburban southwestern Ohio. Despite relatively modest hatching asynchrony, nestling hatch rank (along with brood size and brood age) was an important predictor of the amount of aggression exhibited by individual nestlings. The oldest nestlings exhibited more aggressive behavior than younger nestlings, although they did not consume significantly more food. Aggression rates were higher in broods of three than broods of two nestlings, and aggression decreased from week 2 to week 3, post-hatching. However, hatch rank was not an important determinant of nestling food consumption, and food consumption rates were unrelated to sibling aggression rates. Identifiable prey delivered to nestling Red-shouldered Hawks was diverse and consisted of 28.3% birds, 25.7% mammals, 23.4% amphibians, 16.4% reptiles, and 6.2% invertebrates (by biomass). The relatively high percentage of birds in the diet may reflect food availability in the suburban habitat surrounding the nests. Sibling aggression did not result in direct siblicide in our study, but four nestlings apparently starved. Overall, the oldest Red-shouldered Hawk nestlings in our study established their dominance early but this was not associated with a detectable advantage in terms of food consumption. RESUMEN. En muchas especies de aves rapaces, la asincronía en la eclosión da como resultado una jerarquía de tamaño entre los polluelos, lo que puede facilitar la reducción de la nidada por medio de la mortalidad inducida por la agresión entre hermanos, especialmente en épocas de bajos recursos alimenticios. Sin embargo, pocos investigadores han estudiado las relaciones entre la asincronía en la eclosión, la agresión entre hermanos y las tasas de alimentación de los polluelos en las aves rapaces. Estudiamos la influencia del ranking de eclosión, el tamaño de la nidada y la edad de la nidada en la agresión y las tasas de alimentación entre polluelos de Buteo lineatus en los suburbios del suroeste de Ohio. A pesar de una asincronía en la eclosión relativamente moderada, el ranking de eclosión de los polluelos (junto con el tamaño y la edad de la nidada) fue un predictor importante de la cantidad de agresión exhibida por los polluelos individuales. Los polluelos mayores exhibieron un comportamiento más agresivo que los polluelos más jóvenes, aunque no recibieron una cantidad significativamente mayor de alimento. Las tasas de agresión fueron más altas en las nidadas de tres que en las nidadas d","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86240783","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":"First Biochemical Comparison Between Saker Falcon Subspecies Falco cherrug cherrug and Falco cherrug milvipes","authors":"R. Petrov, I. Lazarova, D. Yarkov, Y. Andonova, Stefka Dimitrova","doi":"10.3356/JRR-22-28","DOIUrl":"https://doi.org/10.3356/JRR-22-28","url":null,"abstract":"ABSTRACT. We collected blood samples from 44 Western Saker Falcons (Falco cherrug cherrug) and 68 Eastern Saker Falcons (Falco cherrug milvipes) in captivity at two facilities in Bulgaria to evaluate the health of individuals involved in a reintroduction project, and to gain insight into appropriate veterinary care and treatment of the birds. We compared the values of 18 biochemical parameters between the two subspecies and also between females and males. We found significant differences between the two subspecies for some of the parameters tested; however, they likely resulted from different feeding regimes at the two breeding facilities—one housing most of the Western Saker Falcons and the other all the Eastern Saker Falcons. Further tests should compare the biochemical values between birds of the two subspecies housed in the same facility. We also found significant differences in the biochemistry of female and male falcons across some parameters tested. After 20 yr without a record of Saker Falcons (Falco cherrug) nesting in Bulgaria, this globally endangered species has been successfully breeding there since 2018 as a result of an ongoing reintroduction project. By establishing baseline information on the differences in the biochemistry of Saker Falcons, our research may guide future studies of this rare species and aid veterinary care and treatment of the birds breeding in captivity. RESUMEN. Tomamos muestras de sangre de 44 individuos de Falco cherrug cherrug y de 68 individuos de Falco cherrug milvipes en cautividad en dos instalaciones en Bulgaria para evaluar la salud de los individuos involucrados en un proyecto de reintroducción, y para obtener información sobre los procedimientos de cuidado veterinario y de tratamiento de las aves. Comparamos los valores de 18 parámetros bioquímicos entre las dos subespecies y también entre hembras y machos. Encontramos diferencias significativas entre las dos subespecies para algunos de los parámetros evaluados; sin embargo, probablemente fueron el resultado de diferentes regímenes de alimentación en las dos instalaciones de cría: una albergaba a la mayoría de los individuos de F. c. cherrug y la otra a todos los individuos de F. c. milvipes. Las evaluaciones adicionales deberían comparar los valores bioquímicos entre las aves de las dos subespecies alojadas en la misma instalación. También encontramos diferencias significativas en la bioquímica de individuos machos y hembras en algunos parámetros probados. Después de 20 años sin registros de nidificación de F. cherrug en Bulgaria, esta especie en peligro de extinción a nivel mundial ha estado reproduciéndose exitosamente allí desde 2018 como resultado de un proyecto de reintroducción en curso. Al establecer información de base sobre las diferencias en la bioquímica de F. cherrug, nuestra investigación puede guiar los estudios futuros de esta rara especie y ayudar al cuidado veterinario y al tratamiento de las aves que se reproducen en cautividad. [T","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84227387","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":"Food Habits of the Mountain Hawk-Eagle (Nisaetus nipalensis orientalis) During the Nesting Period in Japan","authors":"M. Abé, Hiroshi K. Nakamura, A. Higuchi, Hirohiko Sano, Chikako Hashimoto","doi":"10.3356/JRR-21-07","DOIUrl":"https://doi.org/10.3356/JRR-21-07","url":null,"abstract":"ABSTRACT. The Mountain Hawk Eagle (Nisaetus nipalensis orientalis) is classified as endangered in Japan and poorly studied throughout its range. We assessed prey fed to a nestling between hatching and fledging (16 April to 31 July) in central Japan. We used a time lapse camera to record prey deliveries and facilitate prey identification, and we estimated prey biomass and energy content across the nesting season. Of 140 prey items delivered to the single nestling, 65 (46.4%) were of five species of snake, 50 (35.7%) were of nine species of birds, 24 (17.1%) were of seven species of mammals, and one was unknown. The diurnal feeding rhythm showed a peak in prey deliveries at midday; all three classes of prey were delivered at various times of the day in a balanced manner. Snakes were especially prominent in the early stages of the brooding period, but diet shifted toward young birds and mammals in the latter half of the season when the prey species' young had become independent of their parents. Snakes made up the greatest percentage of biomass delivered, followed by mammals and then birds. However, mammals provided more energy per g of prey mass than birds and snakes. The adult eagles relied on large snakes awakened from hibernation in early spring, when prey was scarce, and then shifted to mammals with higher energy value during the peak growth period of the eaglet. An additional 233 prey remains collected from 31 other Mountain Hawk-Eagle nests comprised 20 species of birds and 10 species of mammals, and several unidentified snakes. Pooling results, we identified five species of snakes, 24 species of birds, and 14 species of mammals. These results add to the knowledge of the hawk-eagle's diet and will help to inform management of the species. RESUMEN. En Japón, Nisaetus nipalensis orientalis está clasificada como en peligro de extinción y ha sido relativamente poco estudiada en toda su área de distribución. Evaluamos las presas con que alimentaron a un polluelo entre la eclosión y el emplumamiento (16 de abril al 31 de julio) en el centro de Japón. Usamos una cámara rápida (time lapse) para registrar las entregas de presas y facilitar su identificación, y estimamos la biomasa y el contenido de energía de las presas durante la temporada de anidación. De las 140 presas entregadas a un solo polluelo, 65 (46.4%) pertenecieron a cinco especies de serpientes, 50 (35.7%) a nueve especies de aves, 24 (17.1%) a siete especies de mamíferos y una no fue identificada. El ritmo de alimentación diurno mostró un pico en las entregas de presas al mediodía; las tres clases de presas se entregaron en varios momentos del día de manera balanceada. Las serpientes fueron especialmente prominentes en las primeras etapas del período de cría, pero la dieta se desplazó hacia las aves jóvenes y los mamíferos en la segunda mitad de la temporada, cuando los juveniles de las especies presa se independizaron de sus progenitores. Las serpientes constituyeron el mayor porcentaje","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81526223","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":"Ordinal Date and Tree Diameter Influence Swallow-Tailed Kite (Elanoides forficatus) Nest Survival","authors":"K. N. Smith, W. A. Cox, K. Miller, Lauren L. Plussa","doi":"10.3356/JRR-22-69","DOIUrl":"https://doi.org/10.3356/JRR-22-69","url":null,"abstract":"ABSTRACT. Swallow-tailed Kites (Elanoides forficatus) continue to rebound from population declines during the late 19th and early 20th centuries, and they are considered a species of concern in several southeastern states in the United States. During 2018–2019, we located and monitored 132 active Swallow-tailed Kite nests in and around the Corkscrew Regional Ecosystem Watershed Wildlife and Environmental Area in southwest Florida, USA, to determine how nest site characteristics affect nest survival. Including both years, the earliest active nest (with eggs or young) was discovered on 12 March and the latest nest fledged young on 23 July. Modeled survival of nests from the onset of incubation to fledging was 57.7% (95% CI: 44.5–68.9) and apparent nest survival was 48.7%. Daily survival rate was negatively correlated with ordinal date. Consequently, nests initiated early in the nesting season (mid-March) were more than three times as likely to fledge young as nests initiated late in the season (mid-May). Daily nest survival was positively correlated with nest tree diameter at breast height, indicating that Swallow-tailed Kites had greater nest survival when using larger, more mature trees. We found 99.0% (n = 102) of Swallow-tailed Kite nests in south Florida slash pine (Pinus elliottii var. densa) trees and one nest in bald cypress (Taxodium distichum). Trees used for nesting in our study area were among the largest nest trees reported for the species. Our results suggest that the large pine trees and large cypress trees formerly available in old growth bottomland hardwoods and lowland pine forests of the United States may have provided superior nesting opportunities for Swallow-tailed Kites. RESUMEN. Elanoides forficatus continúa recuperándose de las disminuciones poblacionales ocurridas a fines del siglo XIX y principios del XX y se considera una especie de preocupación en conservación en varios estados del sureste de los Estados Unidos. Durante 2018–2019, localizamos y seguimos 132 nidos activos de E. forficatus, dentro y en la periferia del Área de Vida Silvestre y Medio Ambiente de la Cuenca del Ecosistema Regional Corkscrew en el suroeste de Florida, EEUU, con el fin de determinar cómo las características del sitio de anidación afectan la supervivencia de los pollos en el nido. Incluyendo ambos años, nuestro primer nido activo (con huevos o crías) fue descubierto el 12 de marzo y el último volantón dejó el nido el 23 de julio. La supervivencia modelada de los nidos desde el inicio de la incubación hasta el emplumamiento fue del 57.7% (IC al 95%: 44.5–68.9) y la supervivencia aparente del nido fue del 48.7%. La tasa de supervivencia diaria se correlacionó negativamente con la fecha ordinal. En consecuencia, los nidos iniciados temprano en la temporada de anidación (mediados de marzo) tuvieron una probabilidad tres veces mayor de generar jóvenes volantones que los nidos iniciados al final de la temporada (mediados de mayo). La supervivencia di","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84180261","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":"Population Estimates of the Endangered Javan Hawk-Eagle Based on Habitat Distribution Modeling and Patch Occupancy Surveys","authors":"Syartinilia, Y. Mulyani, Rofifah Aulia Suyitno, A. A. Condro, S. Tsuyuki, S. (. V. Balen","doi":"10.3356/jrr-22-16","DOIUrl":"https://doi.org/10.3356/jrr-22-16","url":null,"abstract":"","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80616296","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":"Wilted Wings: A Hunter's Fight for Eagles","authors":"Jeremy A. Buck","doi":"10.3356/jrr-book-review","DOIUrl":"https://doi.org/10.3356/jrr-book-review","url":null,"abstract":"","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45122021","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":"FACTORS INFLUENCING PREVALENCE AND INTENSITY OF HAEMOSPORIDIAN INFECTION IN AMERICAN KESTRELS IN THE NONBREEDING SEASON ON THE BAJA CALIFORNIA PENINSULA, MEXICO","authors":"M. Frixione, R. Rodríguez-Estrella","doi":"10.3356/jrr-22-74","DOIUrl":"https://doi.org/10.3356/jrr-22-74","url":null,"abstract":"\u0000 Overwintering areas can act as reservoirs for haemosporidians, and their blood-sucking vectors may easily survive and flourish in warm climates. The American Kestrel (Falco sparverius) is a small-sized raptor that includes both resident and migratory individuals that overwinter in agriculture areas of the Baja California peninsula, Mexico. We measured and collected blood samples from 54 individual kestrels captured in a fragmented habitat located within a matrix of agricultural and native scrub in the southern part of the peninsula during the autumn and winter of 2018–2019 and 2019–2020. We identified and quantified haemosporidians in blood smears of each individual. We used decision tree classification models of prevalence and intensities of haemosporidians to assess the importance of season, host body size, and environmental characteristics of the capture site (proximity to the nearest infected host, number of ponds used for irrigation, Normalized Difference Vegetation Index [NDVI], distance to the edge of the agricultural matrix, and distance to the nearest city). Overall prevalence was 42.6%, with an average intensity of 2.4 haemosporidian-infected cells per 2000 erythrocytes. Most haemosporidians (91.3%) were identified as Haemoproteus tinnunculi, and the rest as Plasmodium spp. The prevalence of haemosporidians increased with pond availability, the distance from the edge of the agricultural matrix, and the proximity of infected individuals. Parasite intensity increased with the availability of ponds, the distance to the edge of the agriculture matrix, and the NDVI. Spatial and temporal patterns of parasite prevalence and intensity illustrated local infection dynamics, suggesting a complex scenario of haemosporidian transmission in migratory and resident kestrels.","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42796953","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":"SEASONAL ABUNDANCE AND HABITAT ASSOCIATIONS OF AMERICAN KESTRELS ON THE SOUTHERN HIGH PLAINS OF TEXAS","authors":"Kristen Linner-Warren, B. Bibles, C. Boal","doi":"10.3356/jrr-22-22","DOIUrl":"https://doi.org/10.3356/jrr-22-22","url":null,"abstract":"\u0000 American Kestrel (Falco sparverius) populations are generally declining across the species' North American distribution but the population in the Southern High Plains region currently appears to be stable. Historical evidence suggests the region formerly had a low abundance of kestrels, and that their current numbers are due to landscape changes associated with European settlement. We conducted monthly surveys for American Kestrels across 2 yr to estimate seasonal densities and identify land cover associations in the Southern High Plains of Texas. We found an overall estimated density of 0.99 birds/km2 (95% CI = 0.406, 1.582) across the 2-yr period, with seasonal estimated densities highest in autumn and winter (0.92–2.53/km2), and lowest in spring (0.49–0.67/km2). Whereas other studies have found that temperature influenced detection of wintering kestrels, we found an interaction of drought conditions and snow most strongly influenced the number of kestrels in our study area. Kestrels largely used land cover types in proportion to availability but there was some evidence of seasonal shifts. Generally, they tended to avoid cotton fields and sometimes selected for areas with woodlots, abandoned or occupied houses, and barns, all of which likely provided nesting and roosting opportunities. Our study provides the first contemporary assessment of seasonal abundance and habitat associations of American Kestrels in the Southern High Plains, where their presence and abundance has been unintentionally facilitated by landscape changes following settlement. We provide a baseline for population monitoring and studies assessing response to additional landscape changes (e.g., development of wind energy facilities) and a changing climate.","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48477869","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":"EVIDENCE OF CONTINUING DOWNWARD TRENDS IN AMERICAN KESTREL POPULATIONS AND RECOMMENDATIONS FOR RESEARCH INTO CAUSAL FACTORS","authors":"D. M. Bird, John A. Smallwood","doi":"10.3356/jrr-22-35","DOIUrl":"https://doi.org/10.3356/jrr-22-35","url":null,"abstract":"\u0000 We analyzed long-term datasets from nest box programs, Breeding Bird Surveys run by the US Geological Survey, Christmas Bird Counts run by the National Audubon Society, and counts from two key fall migration watch sites, Hawk Mountain Sanctuary and Cape May Hawkwatch. We found that populations of American Kestrels (Falco sparverius) in North America are generally still declining, albeit with some caveats. Some populations are actually increasing, while others are remaining stable. Overall, the magnitude of annual change appears to be decreasing slightly during recent years. To understand potential causes of the decline, we recommend the following courses of action in no particular order: (1) determine whether the increase in Cooper's Hawk (Accipiter cooperii) populations is restricting kestrel distributions by the mere presence of the larger raptor; (2) study the effects of habitat loss and/or degradation on the falcon's wintering range; (3) further investigate on a broader spatial scale whether within-season habitat alterations are creating ecological traps for breeding kestrels; (4) determine the importance of arthropods in the diet of kestrels, especially the long-term population trends and timing of emergence of grasshoppers in relation to kestrel breeding chronology; (5) discover whether rodenticides pose a serious risk to American Kestrels across North America; (6) learn more about possible effects, both direct and indirect, that the use of neonicotinoids may have on kestrels; and (7) continue ongoing studies of the effect of climate change on these birds.","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49353209","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":"THE ROLE OF FOOD QUANTITY AND PREY TYPE IN NESTLING DEVELOPMENT OF AMERICAN KESTRELS","authors":"Allison Cornell, M. Fowler, Courtney Zimmerman, Zainab Khaku, J. Therrien","doi":"10.3356/jrr-22-10","DOIUrl":"https://doi.org/10.3356/jrr-22-10","url":null,"abstract":"\u0000 Diet is an important component of life history that can vary with, and ultimately determine, individual variation in phenotypically plastic traits. American Kestrels (Falco sparverius) generally have low post-fledging survival rates, which suggests a need to better understand what ecological factors, such as diet, influence nestling maturity. The generalist diet of kestrels makes it unlikely that all nestlings in a population receive the same diet. We investigated how breeding phenology and nestling sex ratio interact with diet metrics (diet diversity, percentage of prey types, rate of prey biomass delivery) and relate to nestling maturity (mass, tarsus length, wing length, hematocrit, hemoglobin concentration). We hypothesized that: (1) phenology and nestling sex ratio would correlate with inter-nest diet variation; (2) diet metrics would be predictive of nestling development; and (3) the manipulation of food quantity through food supplementation would lead to nestlings with greater developmental maturity. We found that inter-nest variation in diet was correlated with breeding phenology and nestling sex ratio, independently. However, the variation in diet was unrelated to nestling maturity. In response to food supplementation, kestrel parents decreased their food-provisioning rate, indicating that food quantity regulates parental care. Male nestlings appeared to benefit from supplementation while females did not. Our data demonstrated high inter-brood variation in nestling diet, and suggested that diet variation interacts with sex to influence growth and development of nestlings, which could potentially be linked to population decline.","PeriodicalId":16927,"journal":{"name":"Journal of Raptor Research","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44340161","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}