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American Kestrel (Falco sparverius)

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... American Kestrels are the smallest and most common North American falcon. Their range includes most of North America, except the far northern portions of Alaska and Canada (Smallwood and Bird 2002). Kestrels are commonly found inhabiting open areas with short ground vegetation where it searches for prey from elevated perches and by hovering above the ground. ...
... Kestrels are commonly found inhabiting open areas with short ground vegetation where it searches for prey from elevated perches and by hovering above the ground. Prey consists of arthropods and small vertebrates (Smallwood and Bird 2002). Kestrels are often attracted to areas of human activities because of the open areas created and the numerous perching sites (Smallwood and Bird 2002). ...
... Prey consists of arthropods and small vertebrates (Smallwood and Bird 2002). Kestrels are often attracted to areas of human activities because of the open areas created and the numerous perching sites (Smallwood and Bird 2002). Kestrels are cavity nesters, using the excavated holes of woodpeckers and other natural cavities in trees (Smallwood and Bird 2002). ...
Technical Report
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This Environmental Assessment evaluates ways to resolve conflicts with bird species in Arizona.
... The American kestrel (Falco sparverius) is a widespread species that breeds throughout North America, and populations display continuous variation in migratory strategies along a latitudinal cline, from fully resident southern populations to fully migratory northern populations (Smallwood & Bird, 2002;Smallwood, Causey, et al., 2009). Recent genetic work on kestrels shows that migratory populations have low genetic structure compared to resident populations (Miller, Mullins, Parrish, Walters, & Haig, 2012). ...
... For several decades, American kestrels have been captured and marked via nest box projects and numerous studies have addressed short-distance kestrel dispersal within project areas (Table 1). These studies show kestrels display female-biased dispersal, in which females may disperse nearly twice as far as males, and median dispersal distances are approximately 7 km (Smallwood & Bird, 2002;Steenhof & Heath, 2013). However, studies of kestrel recruitment (Steenhof & Heath, 2013) and demography (Brown & Collopy, 2013, C.J.W. McClure, unpubl. ...
... This relationship between temperature and dispersal could arise because individuals are responding to proximate environmental cues during dispersal movements, or because warmer The effect of sex depended on August maximum temperature, with differences between sexes only occurring at higher temperatures when males dispersed farther than females. This may be because warmer temperatures reduce the costs of LDD to a greater extent in males, either directly by allowing smaller-bodied individuals to more efficiently move greater distances because kestrels are sexually dimorphic and males are smaller than females (Smallwood & Bird, 2002) or indirectly by influencing young males' ability to acquire a territory (Perrin & Mazalov, 1999). We found evidence of a trend towards female-bias in SDD, and it has been well documented that female kestrels disperse farther than males in other short-distance dispersal studies (Jacobs, 1995;Smallwood & Bird, 2002;Steenhof & Heath, 2013). ...
Article
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Dispersal is a critical process influencing population dynamics and responses to global change. Long‐distance dispersal (LDD) can be especially important for gene flow and adaptability, although little is known about the factors influencing LDD because studying large‐scale movements is challenging and LDD tends to be observed less frequently than shorter‐distance dispersal (SDD). We sought to understand patterns of natal dispersal at a large scale, specifically aiming to understand the relative frequency of LDD compared to SDD and correlates of dispersal distances. We used bird banding and encounter data for American kestrels (Falco sparverius) to investigate the effects of sex, migration strategy, population density, weather, year and agricultural land cover on LDD frequency, LDD distance and SDD distance in North America from 1961 to 2015. Nearly half of all natal dispersal (48.9%) was LDD (classified as >30 km), and the likelihood of LDD was positively associated with the proportion of agricultural land cover around natal sites. Correlates of distance differed between LDD and SDD movements. LDD distance was positively correlated with latitude, a proxy for migration strategy, suggesting that migratory individuals disperse farther than residents. Distance of LDD in males was positively associated with maximum summer temperature. We did not find sex‐bias or an effect of population density in LDD distance or frequency. Within SDD, females tended to disperse farther than males, and distance was positively correlated with density. Sampling affected all responses, likely because local studies more frequently capture SDD within study areas. Our findings that LDD occurs at a relatively high frequency and is related to different proximate factors from SDD, including a lack of sex‐bias in LDD, suggest that LDD may be more common than previously reported, and LDD and SDD may be distinct processes rather than two outcomes originating from a single dispersal distribution. To our knowledge, this is the first evidence that LDD and SDD may be separate processes in an avian species, and suggests that environmental change may have different outcomes on the two processes. La dispersión es un proceso crítico que influye en la dinámica de poblaciones y cómo éstas responden al Cambio Global. La dispersión a larga distancia (LDD) puede ser especialmente importante para el flujo de genes y la adaptabilidad, sin embargo se conoce poco sobre los mecanismos que subyacen a la LDD, ya que su estudio a largo plazo es difícil, lo que resulta en una menor frecuencia de observación de LDD en comparación con la dispersión a corta distancia (SDD). Buscamos comprender los patrones de dispersión natal a gran escala, en particular, comparar la frecuencia relativa de LDD versus SDD, así como la correlación entre las distancias de dispersión y diversos factores. Utilizamos datos de anillamiento y avistamiento del Cernícalo Americano (Falco sparverius) para investigar los efectos del sexo, estrategia de migración, densidad poblacional, meteorología, año, y cobertura de tierra agrícola sobre la frecuencia de LDD, y la distancia de LDD y SDD en Norte América para el período 1961–2015. Casi la mitad de la dispersión natal (48.9%) fue LDD (definida como distancia >30 km), y la probabilidad de LDD estuvo positivamente asociada con la proporción de tierra agrícola alrededor de los sitios de cría. Las correlaciones de las distancias fueron diferentes para los desplazamientos LDD y SDD. La distancia LDD estuvo positivamente correlacionada con la latitud, un indicador de la estrategia de migración, lo que sugiere que los individuos migratorios se dispersan más que los residentes. La distancia LDD en machos estuvo positivamente asociada con la temperatura máxima de verano. No encontramos sesgo en el sexo ni efecto de la densidad poblacional sobre la distancia y frecuencia de LDD. Respecto a SDD, las hembras tendieron a dispersarse más que los machos, y la distancia estuvo positivamente correlacionada con la densidad. El muestreo afectó a todas las variables de respuesta analizadas, probablemente debido al hecho de que los estudios a escala local detectan con mayor frecuencia SDD dentro de las áreas de estudio. Nuestro hallazgo referente al hecho de que LDD sucede con relativa alta frecuencia y está controlada por factores diferentes a los de SDD, como por ejemplo, la ausencia de sesgo debido al sexo en LDD, sugiere que LDD puede ser más común de lo propuesto hasta ahora, y que LDD y SDD pueden ser considerados como dos procesos distintos y no como resultados procedentes de una única distribución de dispersión. Hasta donde sabemos, ésta es la primera evidencia de que LDD y SDD pueden ser dos procesos separados en aves, sugiriendo que los cambios ambientales pueden afectarles de manera diferente. The authors assess the relative frequency and correlates of shorter‐distance dispersal (SDD) and long‐distance dispersal (LDD) natal dispersal using banding data. LDD was more frequent than previously reported and correlates of LDD and SDD differed. LDD and SDD may be distinct processes, rather than a single right‐skewed dispersal kernel, and environmental change may influence the two movements differently.
... The American Kestrel (Falco sparverius) is a small falcon widely distributed in America from Alaska and Canada in the north to Tierra del Fuego and Islas Malvinas (Falkland Islands) in the south. It inhabits most natural and modified environments through the continent as long as they contain some open areas; it is not present in heavily forested areas, the tundra, and some areas of the Amazon basin and coastal Brazil (del Hoyo et al. 1994, Ferguson-Lees and Christie 2001, Smallwood and Bird 2002. In Argentina, it occurs throughout the country, occupying almost all ecosystems, being especially abundant in agricultural areas and other open areas (Donázar et al. 1993, De la Peña and Rumboll 1998, Narosky and Yzurieta 2003. ...
... In Argentina, it occurs throughout the country, occupying almost all ecosystems, being especially abundant in agricultural areas and other open areas (Donázar et al. 1993, De la Peña and Rumboll 1998, Narosky and Yzurieta 2003. An opportunist-generalist predator, the kestrel feeds on insects and small vertebrates (Ferguson-Lees and Christie 2001, Smallwood and Bird 2002, Sarasola et al. 2003, Liébana et al. 2009). Its breeding biology has been extensively investigated in North America using both natural nests and nest boxes (Smallwood and Bird 2002), but little studied in South America (Balgooyen 1989, De Lucca and Saggese 1993, Sarasola et al. 2003, Liébana 2008, Santillán et al. 2009, Liébana et al. 2013). ...
... Its breeding biology has been extensively investigated in North America using both natural nests and nest boxes (Smallwood and Bird 2002), but little studied in South America (Balgooyen 1989, De Lucca and Saggese 1993, Sarasola et al. 2003, Liébana 2008, Santillán et al. 2009, Liébana et al. 2013). In the northern hemisphere, where several largescale long-term studies have been conducted, clutch sizes usually range from four to six eggs, with rare extreme ranges of 1-7 and a single record of eight eggs that was discounted because it was presumed to be the product of two females Palmer 1988, Smallwood andBird 2002). As an example, Wiebe and Bortolotti (1995) studied 1124 clutches during 3 yr in Saskatchewan and found only 48 clutches of six eggs (4.3%) and none of seven or eight. ...
... Beginning in early March 2014, nest boxes were checked weekly to monitor their use by kestrels. Because female kestrels typically begin egg laying during the period from late March to April (Smallwood and Bird, 2002), nest boxes were checked every two or three days beginning on 1 April with a TreeTop Peeper (Sandpiper Technologies, Inc., Manteca, CA) for the presence of eggs. Nests that had eggs for 20 days were then checked every one to two days for hatching, and date of first hatching was recorded to estimate age of nestlings during experiments. ...
... Each nest was randomly assigned a single treatment. Video recording occurred when nestling ages were 12 to 26 days post-hatching; growth rates of nestlings are most rapid from about day 7 to days 18-20 post-hatching, then reach an asymptote (Smallwood and Bird, 2002). Young kestrels typically fledge from nests 28 to 31 days after hatching (Smallwood and Bird, 2002). ...
... Video recording occurred when nestling ages were 12 to 26 days post-hatching; growth rates of nestlings are most rapid from about day 7 to days 18-20 post-hatching, then reach an asymptote (Smallwood and Bird, 2002). Young kestrels typically fledge from nests 28 to 31 days after hatching (Smallwood and Bird, 2002). ...
Article
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Little is known about how variation in nestling begging intensity influences the behaviour of adult raptors and how responses of adult males and females to such variation might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adults. We studied 12 pairs of American Kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behaviour, and a second camcorder was placed outside the nests to monitor adult behaviour. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 h and those in the other six nests were fed until satiated. At each nest, we alternated control (no treatment) and treatment (fed or food deprived) days over a 4 day period to minimise the possible effect of nestling age on adult and nestling behaviour. Nestling begging intensity differed among treatments, with nestlings in food-deprived nests begging with greater intensity after food deprivation and those in fed-treatment nests begging with less intensity after being fed. Adult male and female American Kestrels provisioned nestlings at similar rates, with both sexes feeding nestlings at higher rates after food deprivation and at lower rates after fed treatments. Thus, the begging behaviour of nestling American Kestrels varied with hunger level, and adult American Kestrels responded by adjusting provisioning rates. Although the response of adults to nestling begging suggests that natural selection might favour 'dishonest' begging to obtain more food, the potential costs of 'dishonest' begging, such as attracting predators, reduced immunocompetence, and loss of indirect fitness benefits if such begging negatively impacts siblings and parents, may outweigh any possible benefit.
... We examined sex differences in hippocampus volume relative to telecephalon volume (measure of forebrain size) and brain weight of hatchling American kestrels (Falco sparverius; hereafter "kestrel"). As adults, kestrels show moderate sexual size dimorphism, with females being 15-20% larger than males at the level of the subspecies [16,17]. Kestrels are North America's smallest falcon, with males weighing 100 g and (non-breeding) females 120 g, feeding primarily on insects and other invertebrates, as well as on small rodents and birds (e.g., voles, sparrows, warblers) [17]. ...
... As adults, kestrels show moderate sexual size dimorphism, with females being 15-20% larger than males at the level of the subspecies [16,17]. Kestrels are North America's smallest falcon, with males weighing 100 g and (non-breeding) females 120 g, feeding primarily on insects and other invertebrates, as well as on small rodents and birds (e.g., voles, sparrows, warblers) [17]. However, kestrels can hunt larger prey, including squirrels and woodpeckers [16,17]. ...
... Kestrels are North America's smallest falcon, with males weighing 100 g and (non-breeding) females 120 g, feeding primarily on insects and other invertebrates, as well as on small rodents and birds (e.g., voles, sparrows, warblers) [17]. However, kestrels can hunt larger prey, including squirrels and woodpeckers [16,17]. Compared to females, male kestrels hunt more birds [18], a more agile prey type than mammals such as rodents. ...
Article
The brain and underlying cognition may vary adaptively according to an organism's ecology. As with all raptor species, adult American kestrels (Falco sparverius) are sexually dimorphic with females being larger than males. Related to this sexual dimorphism, kestrels display sex differences in hunting and migration, with females ranging more widely than males, suggesting possible sex differences in spatial cognition. However, hippocampus volume, the brain region responsible for spatial cognition, has not been investigated in raptors. Here, we measured hippocampus and telencephalon volumes in American kestrel hatchlings and found no significant difference between left and right hemispheres for either hippocampus or telencephalon. Female hatchlings had a significantly larger hippocampus relative to the telencephalon and brain weight than males (~12% larger), although telencephalon volume relative to brain weight and body size was similar between the sexes. The magnitude of this hippocampal sex difference is similar to that reported between male and female polygynous Microtus voles and subspecies of Zonotrichia sparrows. Future research should determine if this sex difference in relative hippocampus volume of hatchling kestrels persists into adulthood and if similar patterns exist in other raptor species, thus potentially linking sex differences in the brain to sex differences of space use of adults in the wild.
... American Kestrels are known to be raptors of open habitats, so we hypothesised that they would respond negatively to loss of sandhill and other open habitats (Smallwood and Bird 2002 ). Because the extent of sandhill habitat has decreased throughout Florida since the initiation of the kestrel nest box project, we predicted that some boxes which were once located in sandhill habitat were likely to be surrounded by less suitable habitats later, with the net result that the overall occupancy rates of nest boxes will have decreased over time. ...
... Boxes were considered occupied only if either eggs or nestling kestrels were found, even though adult kestrels may have been detected in the area. We checked most boxes through July or August, but here we consider observations between March and June as the majority of nesting attempts were initiated in these months (Smallwood and Bird 2002 ). Research and handling protocols (#00329) were reviewed and approved by the Institutional Animal Care and Use Committee at the University of Nevada, Reno. ...
... Configuration and form of habitats thought to be important to kestrels in the reclassified maps were quantified in the program FRAGSTATS (McGarigal et al. 2002 ). Moving window analyses generated class and landscape metric surfaces that integrated landscape characteristics at two biologically relevant scales, reflecting a potential home range size (1-km diameter circle) and median natal dispersal distance (4.9-km diameter circle) respectively Bird 2002 ). Metrics were selected to represent universal and highly consistent components of class-level and landscape-level structure as identified by Cushman et al. ( 2008 ). ...
Article
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Despite the recent rapid decline of many grassland bird species, the relative importance of habitat configuration to population persistence is unclear. We used Southeastern American Kestrels Falco sparverius paulus in north-central Florida as a model system to explore the relative influence of landscape structure components on site occupancy patterns at two spatial scales, and for two different time periods. We focused on the dynamic processes of site-level population expansion or contraction. We modelled the occupancy of 131 American Kestrel nest boxes with Bayesian state- space dynamic occupancy models that considered both the partially observed process of true occupancy and the probability of detection of occupancy. We used reversible jump Markov chain Monte Carlo (RJMCMC) algorithms to identify variables that described the continued occupancy of nest boxes, or phi, and the probability of colonisation of nest boxes between time periods, or gamma(3) Changes in open habitat patch isolation at a fine scale, as estimated by the variability of nearest neighbour distance, predicted site colonisation between decades, and patch shape variability was related to phi during the early time period (1992-93). We found no strong effects of landscape structure on phi during the later time period (2008-2010). We also found no evidence for effects of loss of open habitat on box occupancy or colonization. Our results indicate that continued habitat fragmentation would be deleterious for this threatened subspecies. Additionally, certain land cover management practices recommended for the Florida sandhills, such as frequent low-intensity controlled burns, will likely help conservation attempts.
... Southward migration begins in mid-August; by the last week in October the southernmost watch sites in New Mexico have counted Ͼ 90% of their total kestrel observations (Smith and Neal 2009). Th e timing of southward migration may be limited by completion of a post-nesting molt, which may cause adults to migrate later than juveniles (Smallwood and Bird 2002). Kestrels defend winter territories and early-arriving birds occupy higher quality overwintering sites than late-arriving birds (Smallwood and Bird 2002). ...
... Th e timing of southward migration may be limited by completion of a post-nesting molt, which may cause adults to migrate later than juveniles (Smallwood and Bird 2002). Kestrels defend winter territories and early-arriving birds occupy higher quality overwintering sites than late-arriving birds (Smallwood and Bird 2002). Northward migration begins in early March and most kestrels arrive on their nesting grounds by 1 April (Henny 1972), although nesting may begin earlier at southern sites (Smallwood and Bird 2002). ...
... Kestrels defend winter territories and early-arriving birds occupy higher quality overwintering sites than late-arriving birds (Smallwood and Bird 2002). Northward migration begins in early March and most kestrels arrive on their nesting grounds by 1 April (Henny 1972), although nesting may begin earlier at southern sites (Smallwood and Bird 2002). Th e migration study area boundaries were the Pacifi c Ocean in the west and the Rocky Mountains in the east. ...
Article
Global climate change has affected avian migration patterns and nesting phenology. Changes in one phase of a bird's cycle will most likely affect other stages, but few studies focus simultaneously on multiple life-history events. We used western North American ringing records and Christmas Bird Counts to examine whether changes in migration patterns were concordant with advancing American kestrel Falco sparverius nesting phenology. Consistent with previous findings, male kestrels migrated shorter distances than female kestrels, and kestrels nesting in southern latitudes migrated shorter distances than kestrels nesting in more northern areas. In addition, kestrel migration distance decreased significantly from 1960 to 2009 and was negatively associated with winter minimum temperatures. Christmas Birds Counts from the same time period showed increasing indices of overwintering kestrel abundance in northern states (Washington, Idaho, and Utah), where winter minimum temperatures have increased significantly, and concomitant decreases in southern states (California and Arizona). Finally, changes in nesting phenology of kestrels in southwestern Idaho were best explained by warmer winters, not springs. Warmer winters may decrease energetic demands on migrants by allowing for shorter migration distances, decreasing thermoregulatory costs, or both. Decreased energy demands during winter may allow birds to gain resources necessary for reproduction earlier in the nesting season. Higher winter temperatures that decrease (former) constraints on early nesting may be a particularly important mechanism leading to advancing nesting phenology for species with strong seasonal declines in fecundity or intense early season competition for high-quality nesting areas.
... These differences may be due to the small sample size analyzed in previous studies since both, Liébana et al. 45 and De Lucca and Saggesse 46 only monitored sixs nest during a single breeding season, contrasting with the 457 reproductive events monitored over 6 breeding seasons in the present study. On the other hand, the results of this study also coincided with the general reproductive parameters reported for the American kestrels in the northern hemisphere 16,47 . ...
... Nest box occupation by American kestrels in both agricultural farmlands (traditional and intensive) was greater than in PLNR. American kestrels prefer nests located in open habitats 47 and some nest boxes in PLNR Table 2. Nest box occupancy by American kestrels among sampling areas (Parque Luro Natural Reserve, Traditional farmland and, Intensive farmland) between 2011 and 2016 in La Pampa, central Argentina. Nest boxes in intensive agricultural areas were placed in the year 2012. ...
... The low occupancy of nest boxes in Caldén forest (from around 17% to 50%) could also reflect the high availability of alternative breeding sites there. The American kestrel is a secondary cavity nester and thus its populations could be limited by cavity availability 47 . In Parque Luro Natural Reserve, the forest covers more than 70% of the surface (Fig. 1) and thus, kestrels have high availability of alternative nesting sites like tree cavities and nests of Monk parakeets (Myiopsitta monachus) and Brown cacholotes (Pseidoseisura lophotes), that are also used by the species to breed 49,50 . ...
Article
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Land-use changes due to agricultural intensification and climatic factors can affect avian reproduction. We use a top predator of agroecosystems, the American kestrel (Falco sparverius) breeding in nest boxes in Central Argentina as a study subject to identify if these two drivers interact to affect birds breeding. We analyzed their breeding performance across a gradient of agricultural intensification from native forest, traditional farmland to intensive farmland. The surface devoted to soybean was used as a proxy of agriculture intensification; however, it did not affect the breeding performance of American kestrels. Even though the presence of pastures was important to determine the probability of breeding successfully. Climatic variables had strong effects on the species breeding timing, on the number of nestlings raised by breeding pairs and on the probability of those pairs to breed successfully (raising at least one fledgling). Our results highlight the relevance of pastures and grasslands for American kestrel reproduction. These environments are the most affected by land-use change to intensive agriculture, being transformed into fully agricultural lands mostly devoted to soybean production. Therefore, future expansion of intensive agriculture may negatively affect the average reproductive parameters of American Kestrels, at least at a regional scale. Further research will be needed to disentangle the mechanisms by which weather variables affect kestrel breeding parameters.
... For example, songbird males involved in extra-pair copulations with larger song-repertoire sizes, have more offspring and their offspring are more likely to survive, than males with smaller song-repertoire sizes (Hasselquist et al., 1996). Birds that do not sing, such as raptors, will emit vocalizations indicative of "friendly" approaches between members of the pair (Smallwood and Bird, 2002), and these are important for establishing the pair-bond and determining the quality of the pair-bond. Non-vocal interactions between members of a pair, such as courtship displays, may also affect reproduction. ...
... Non-vocal interactions between members of a pair, such as courtship displays, may also affect reproduction. For example, male American kestrels that spend more time with their mate copulate more frequently (Smallwood and Bird, 2002). Another behavioural endpoint closely related to reproduction is nest or incubation temperature; the more time adults spend incubating their clutch, the higher the nest temperature. ...
Article
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Flame retardants (FRs) are a diverse group of chemicals, many of which persist in the environment and bioaccumulate in biota. Although some FRs have been withdrawn from manufacturing and commerce (e.g., legacy FRs), many continue to be detected in the environment; moreover, their replacements and/or other novel FRs are also detected in biota. Here, we review and summarize the literature on the toxic effects of various FRs on birds. Birds integrate chemical information (exposure, effects) across space and time, making them ideal sentinels of environmental contamination. Following an adverse outcome pathway (AOP) approach, we synthesized information on 8 of the most commonly reported endpoints in avian FR toxicity research: molecular measures, thyroid-related measures, steroids, retinol, brain anatomy, behaviour, growth and development, and reproduction. We then identified which of these endpoints appear more/most sensitive to FR exposure, as determined by the frequency of significant effects across avian studies. The avian thyroid system, largely characterized by inconsistent changes in circulating thyroid hormones that were the only measure in many such studies, appears to be moderately sensitive to FR exposure relative to the other endpoints; circulating thyroid hormones, after reproductive measures, being the most frequently examined endpoint. A more comprehensive examination with concurrent measurements of multiple thyroid endpoints (e.g., thyroid gland, deiodinase enzymes) is recommended for future studies to more fully understand potential avian thyroid toxicity of FRs. More research is required to determine the effects of various FRs on avian retinol concentrations, inconsistently sensitive across species, and to concurrently assess multiple steroid hormones. Behaviour related to courtship and reproduction was the most sensitive of all selected endpoints, with significant effects recorded in every study. Among domesticated species (Galliformes), raptors (Accipitriformes and Falconiformes), songbirds (Passeriformes), and other species of birds (e.g. gulls), raptors seem to be the most sensitive to FR exposure across these measurements. We recommend that future avian research connect biochemical disruptions and changes in the brain to ecologically relevant endpoints, such as behaviour and reproduction. Moreover, connecting in vivo endpoints with molecular endpoints for non-domesticated avian species is also highly important, and essential to linking FR exposure with reduced fitness and population-level effects.
... In contrast to the Cooper's Hawk, Sharp- shinned Hawks from the central flyway moved farther than eastern and western Sharp-shinned Hawks. The complex patterns observed could be due in part to the differences in species' ranges (Rosenfield and Evans 1980, Bildstein and Meyer 2000, Smallwood and Bird 2002 and how we pooled the data into three flyways. In the west, coastal birds often migrate shorter distances compared with inland-nesting birds (Goodrich and Smith 2008). ...
... Average migration distances in this species differed between males and females, with males staying closer to breeding latitudes than females. This supported the suggestion (Smallwood and Bird 2002) that males generally winter closer to the breeding grounds than females in this species. The decrease in movement across the years studied deserves further monitoring and research in the future. ...
Article
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We examined banding encounter records from 1920 to 2006 for three raptors that are commonly banded in North America: American Kestrel (Falco sparverius, 4707 encounters), Sharp-shinned Hawk (Accipiter striatus; 5256), and Cooper's Hawk (A. cooperii; 3848). We selected birds banded during summer or autumn migration and encountered during winter to investigate movement distances and winter latitudes by sex, age, year banded, banding latitude, and flyway. Female American Kestrels migrated farther than males, but travel distances did not vary by age. Distance moved to wintering sites declined with encounter year for American Kestrels, suggesting that migratory short-stopping may be occurring across North America. Movements of the three species typically showed a chain migration pattern; however, female American Kestrels from the most northern latitudes demonstrated a leapfrog pattern, moving beyond mid-latitude birds to more southerly wintering latitudes. Female American Kestrels and Cooper's Hawks moved farther than males, whereas Sharp-shinned Hawk migration distances did not vary by sex. Hatch-year Sharp-shinned and Cooper's hawks moved farther than after-hatch-year birds, whereas no age difference was observed for American Kestrels. For all three species, northern-latitude birds moved farther than mid- or low-latitude birds, and low-latitude birds appeared to be largely resident. Distances moved also varied by flyway for both accipiters.
... The male begins transferring food to the female 4-5 weeks prior to laying. The female typically lays one egg a day and incubation begins upon laying the second to last egg (Smallwood and Bird 2002). Clutch size is usually 3 to 5 eggs. ...
... obs.). This decline may be associated with an increase in mortality during the non-breeding season due to the suitability of their wintering grounds (Smallwood and Bird 2002). The widespread decline in kestrel populations cannot be accredited to a single factor but it must be taken into consideration the importance of creating nesting habitats for them. ...
Technical Report
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In spring 2014, the Reserve initiated a conservation project to expand American Kestrel (Falco sparverius) nesting populations into the Merced Vernal Pools and Grassland Reserve and to monitor their breeding success. Kestrels are common nesting birds in eastern Merced County, but there was no evidence that they currently nested in the Reserve. Kestrels are often seen foraging in the Reserve; we have observed them on 45 of 105 bird surveys conducted between January 2013 and August 2014 (Swarth unpubl. data). The maximum observed on one day was 12 in July 2013. The 6,500 acres in the Reserve represent a vast area of suitable nesting habitat for this small falcon. Table 2 indicates the clutch size, fate and productivity of the ten nests. Six of ten nests held eggs. Clutch size varied from 2 to 5 eggs. There were a total of 22 eggs in the 6 nests. Nests KB6 and KB8 had eggs, but failed to produce chicks. eggs were collected. Their dimensions were 32 mm X 29 mm and 35 mm X 28 mm.
... March through late June with a peak in late April (Smallwood & Bird, 2002). Prior to clutch initiation, pairs must establish and defend their territory and may use the perches to do so. ...
... Nonetheless, up to three individuals have been reported using artificial perches concurrently in the same field without incident (Hall et al., 1981). Additionally, while interspecific predation among our three focal species has been reported, artificial perches are unlikely to greatly increase the risk of predation (Petersen, 1979;Smallwood & Bird, 2002). Indeed, red-tailed hawk and great horned owl breeding territories often overlap without incident (Artuso et al., 2013). ...
Article
Cover crops are an increasingly common conservation practice in intensive row‐crop agriculture of the Midwestern United States and can improve wildlife habitat. However, they also benefit agricultural pest species such as voles (Microtus ), which have damaged cover‐cropped soybean fields in Indiana. We tested the feasibility of attracting raptors, which are natural predators of voles, to cover‐cropped fields by supplying artificial perches from which to hunt. We assessed raptor use of artificial perches in cover‐cropped fields during the winters of 2018 and 2019. Perches were erected at 3 different distances from the field edge: 50, 125, and 200m. We modeled perch use of our 3 most common species, great horned owl, red‐tailed hawk, and American kestrel, with a logistic generalized linear mixed model. Raptors used 82% of the perches, and perch use was greatest at 200 m. However, even at peak use, our best model predicted a low probability of overall perch use for all three species. Artificial perches can attract raptors into large row‐crop fields. Sturdier perch design, extended perch availability, and greater vole populations could increase use of perches. Although raptor perch use by itself is unlikely to control vole populations in cover‐cropped fields, artificial perches could form a valuable component of an integrated pest management system. This article is protected by copyright. All rights reserved.
... American kestrels Falco sparverius (Linnaeus 1758) are a widespread, cavity-nesting falcon that occurs in a variety of human-dominated landscapes including urban, suburban and agricultural habitats (Smallwood & Bird 2002). Kestrels are considered a human-tolerant species (Smallwood & Bird 2002); however, use of humandominated areas may make kestrels susceptible to noxious anthropogenic stimuli that negatively affect survival or reproductive success. ...
... American kestrels Falco sparverius (Linnaeus 1758) are a widespread, cavity-nesting falcon that occurs in a variety of human-dominated landscapes including urban, suburban and agricultural habitats (Smallwood & Bird 2002). Kestrels are considered a human-tolerant species (Smallwood & Bird 2002); however, use of humandominated areas may make kestrels susceptible to noxious anthropogenic stimuli that negatively affect survival or reproductive success. Further, kestrel populations are declining in parts of their range, and the cause of this decline is poorly understood (Farmer & Smith 2009). ...
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The rapid increase of human activity in wild and developed areas presents novel challenges for wildlife. Some species may use human-dominated landscapes because of favourable resources (e.g. high prey availability along roadsides); however, use of these areas may increase exposure to anthropogenic stressors, such as human disturbance or noise, which can negatively affect reproduction or survival. In this case, human-dominated landscapes may act as an ecological trap.We evaluated whether American kestrel Falco sparverius reproductive failure was associated with human disturbance (traffic conditions and land development) or other common predictors of reproductive outcome, such as habitat and clutch initiation date. Also, we examined relationships among human disturbance, corticosterone (CORT) concentrations and nest abandonment to explore potential mechanisms for stress-induced reproductive failure.Twenty-six (36%) of 73 kestrel nesting attempts failed and 88% of failures occurred during incubation. Kestrels nesting in higher disturbance areas were 9·9 times more likely to fail than kestrels nesting in lower disturbance areas. Habitat and clutch initiation date did not explain reproductive outcome.Females in higher disturbance areas had higher CORT and were more likely to abandon nests than females in lower disturbance areas. There was no relationship between male CORT and disturbance or abandonment. Females spent more time incubating than males and may have had more exposure to anthropogenic stressors. Specifically, traffic noise may affect a cavity-nesting bird's perception of the outside environment by masking auditory cues. In response, incubating birds may perceive a greater predation risk, increase vigilance behaviour, decrease parental care, or both.Synthesis and applications. Proximity to large, busy roads and developed areas negatively affected kestrel reproduction by causing increased stress hormones that promoted nest abandonment. These results demonstrate that species presence in a human-dominated landscape does not necessarily indicate a tolerance for anthropogenic stressors. Managers should carefully consider or discourage projects that juxtapose favourable habitat conditions with areas of high human activity to decrease risk of ecological traps. Noise mitigation, while locally effective, may not protect widespread populations from the pervasive threat of traffic noise. Innovative engineering that decreases anthropogenic noise at its source is necessary.
... The Burrowing Owl (Athene cunicularia, Molina 1782) and the American Kestrel (Falco sparverius, Linnaeus 1758) are small-sized (Smallwood and Bird 2002;Poulin et al. 2020), wide-ranging -from southern Argentina to Canada -raptors that inhabit open plains (Desmond et al. 2000;Conway et al. 2012). Population trends of the Burrowing Owl show local variations across North America, and in northwestern Mexico the species has been colonising agricultural landscapes lately, increasing in occurrence on agriculture and surrounding habitats in the Baja California peninsula (Macías-Duarte 2011;Macías-Duarte and Conway 2015). ...
... Morphology of these two raptors is similar, and differences in body mass between Burrowing owls and American kestrels are not as significant as between other raptors (A. cunicularia: 150-170 g mean weight; F. sparverius, 110-129 g mean weight; Smallwood and Bird 2002;Poulin et al. 2020). ...
Article
We analysed the diet of the Burrowing Owl (Athene cunicularia) and the American Kestrel (Falco sparverius) in a fragmented habitat and natural surroundings in the arid ecosystem of the Baja California peninsula, Mexico. Both small-sized raptors are considered in the same trophic guild, and as keystone species, interactions between them could be of interest for wildlife management in fragmented landscapes for agricultural activities. The diet analysis of these top predators could be a good monitor of prey abundance, some of which may be considered detrimental for agricultural activities. Prey frequencies in owl pellets were higher for arthropods (53.1%) and rodents (32.4%), but rodents were the most abundant item in terms of biomass (34.5%). Arthropods also showed higher relative frequencies in kestrel pellets (36.4%), but reptiles were the second in order of importance (28.4%) and contributed the most (64.7%) to the total prey biomass. The biomass contribution (66.1%) of vertebrates in the diet of the Burrowing Owl was lower than for the American Kestrel (95.6%) in a fragmented habitat area. Most prey types were present in the diet of both raptors, but we found significant differences in the biomass contributions of each category. Reptiles and rodents were the prey items that contributed most to the differences in the raptors’ diets, in terms of biomass (33% and 20.3%, respectively). Close nesting surroundings (0.5 km and 1 km radius) evidenced a higher proportion of natural vegetation in the kestrel’s (50.6% and 38.9%, respectively) than in owl’s potential home range (25.8% and 16.4%). The differences in diet suggest some degree of niche partitioning of these species likely due to the more flexible owl’s nesting habitat requirements and to the extended nocturnal activity of the species. These results reflect the capability of being complementary species, both exploiting some pests that are harmful for agriculture, and evidencing the importance of both species as regulators of agro-ecosystems in the peninsula of Baja California.
... The American Kestrel (Falco sparverius) is a small, socially monogamous, and sexually dimorphic raptor that occurs throughout North and South America (Smallwood and Bird 2002). It is common in habitats used and modified by humans, and, as a secondary cavity nester, it readily uses nest boxes. ...
... We assumed that adults trapped at boxes were the parents of the young in boxes. The frequency of extra-pair copulations in the American Kestrel is low (Villarroel et al. 1998), and brood parasitism has never been documented in the species (Smallwood and Bird 2002). We had no evidence for trios (e.g., Towers 1990), so it is likely that nearly all adults were the true genetic parents of the eggs and young that they tended. ...
Article
Variation in recruitment patterns and dispersal behavior can have important consequences for population viability, genetic structure, and rates of evolutionary change. From 1992 to 2006 we studied a marked population of American Kestrels (Falco sparverius) nesting in boxes in southwestern Idaho to identify factors that affect local recruitment and natal dispersal distances. A low proportion (4%) of locally produced kestrels (n = 2180) returned to nest in study area boxes. Offspring of locally produced individuals were 3.1 times more likely to return than offspring of parents that did not hatch in study area boxes and, independent of a parent's origin, males were 1.8 times more likely than females to return. Kestrels that hatched earlier in the breeding season and those that hatched immediately prior to a mild winter were more likely to return. Local natal dispersal distances were best explained by sex and parental origin but not by hatching dates. Fifty-four males moved an average of 5.3 km from their natal box to the location of their first breeding in the study area, and 27 females moved an average of 9.8 km. Offspring of locally produced parents dispersed shorter distances within the study area than offspring of other parents, and local natal dispersal distances of locally produced parents correlated with those of their same-sex offspring. Patterns of natal dispersal of American Kestrels in southwestern Idaho appear to be driven by a combination of parental dispersal tendencies and ecological factors. The population consists of a mix of immigrants and philopatric birds.
... Here we use next-generation sequencing (NGS) technology to create a genoscape for the American Kestrel, assess its relationship to current subspecies boundaries, and provide a framework for conservation and management of this and other highly mobile species with a high capacity for dispersal. The American Kestrel (Falco sparverius) is a widely distributed species that breeds throughout North and South America (Smallwood and Bird 2020) and has upwards of 17 recognized subspecies (Ferguson-Lees and Christie 2006). American Kestrels show highly variable migration strategies across their range, including individuals that migrate long distances, short distances, or do not migrate, and populations that are completely migratory, partially migratory, or non-migratory (Layne 1982, Bird and Palmer 1988, Henny and Brady 1994, Smallwood and Bird 2020. ...
... The American Kestrel (Falco sparverius) is a widely distributed species that breeds throughout North and South America (Smallwood and Bird 2020) and has upwards of 17 recognized subspecies (Ferguson-Lees and Christie 2006). American Kestrels show highly variable migration strategies across their range, including individuals that migrate long distances, short distances, or do not migrate, and populations that are completely migratory, partially migratory, or non-migratory (Layne 1982, Bird and Palmer 1988, Henny and Brady 1994, Smallwood and Bird 2020. Here we focus on 2 American Kestrel subspecies found north of the Mexico and U.S. border, the non-migratory subspecies (F. ...
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Identifying population genetic structure is useful for inferring evolutionary process and comparing the resulting structure with subspecies boundaries can aid in species management. The American Kestrel (Falco sparverius) is a widespread and highly diverse species with 17 total subspecies, only 2 of which are found north of U.S./Mexico border (F. s. paulus is restricted to southeastern United States, while F. s. sparverius breeds across the remainder of the U.S. and Canadian distribution). In many parts of their U.S. and Canadian range, American Kestrels have been declining, but it has been difficult to interpret demographic trends without a clearer understanding of gene flow among populations. Here we sequence the first American Kestrel genome and scan the genome of 197 individuals from 12 sampling locations across the United States and Canada in order to identify population structure. To validate signatures of population structure and fill in sampling gaps across the U.S. and Canadian range, we screened 192 outlier loci in an additional 376 samples from 34 sampling locations. Overall, our analyses support the existence of 5 genetically distinct populations of American Kestrels—eastern, western, Texas, Florida, and Alaska. Interestingly, we found that while our genome-wide genetic data support the existence of previously described subspecies boundaries in the United States and Canada, genetic differences across the sampled range correlate more with putative migratory phenotypes (resident, long-distance, and short-distance migrants) rather than a priori described subspecies boundaries per se. Based on our results, we suggest the resulting 5 genetically distinct populations serve as the foundation for American Kestrel conservation and management in the face of future threats.
... The kestrel's recruitment and rates of return to breeding areas are generally low Bird 2002, but see Balgooyen 1976) so its movement within and among years is difficult to describe. In the population we studied, located in north-central Saskatchewan, kestrels molt their primary flight feathers once per year, during breeding (Smallwood and Bird 2002). Therefore, the δD of primaries collected before molt in the current breeding season should reflect the approximate location of growth in the preceding nesting season. ...
... If this feather was already molted, we sampled from the left wing or clipped the 5 th primary if the 4 th was molted from both sides. The kestrel's molt begins with the 4 th primary and proceeds in both directions (Smallwood and Bird 2002); at our study area this begins during breeding, usually during incubation. We used this first-molted feather to ensure we obtained one that was grown at the location of breeding. ...
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Many populations of the American Kestrel (Falco sparverius) are in decline; in northern populations it is unknown whether low recruitment and rates of return are due to mortality, poor detection, or dispersal. Ratios of stable hydrogen isotopes in feathers (δDf) have been used widely to estimate origins of birds, in some cases providing estimates of adults dispersal between breeding seasons and post-natal dispersal of young. We attempted to use δD in feathers, grown during breeding, to identify returning and immigrant birds and to quantify dispersal. We used birds of known origin to establish the expected local δDf but found a high degree of deuterium enrichment in these individuals relative to the local δD of rainfall (δDP) and a significant difference between δDf of nestlings and adults, which complicated the distinguishing of local birds from immigrants. We subsequently compared the δD of primary feathers and plasma of adults and tested for relationships among the δD of adult feathers and adult mass, body size, and reproductive effort at the time of growth to explore the cause of deuterium enrichment in adult feathers. Adults' feathers were significantly more deuterium-enriched than plasma, and their distribution did not overlap with that of nestlings' feathers. Larger males and females that fledged female nestlings of greater mass had feathers that were more deuterium-enriched, while males whose mates laid clutches of greater volume had less enriched feathers. We discuss our results with respect to the prevailing hypotheses for deuterium enrichment of raptor feathers, particularly the evaporative-cooling hypothesis.
... American kestrels (Falco sparverius) are a widespread, generalist predator that breeds across much of North America. They have broad diets and prey on insects, small mammals, birds, and lizards (Smallwood & Bird, 2020), and start of spring is a good proxy for abundance (which was not certified by peer review) is the author/funder. All rights reserved. ...
... ~ 4 month lay date range in southwestern Idaho; Steenhof & Peterson, 2009). Less is known about kestrel demographics in the Southwest, but southern populations are less migratory (Smallwood & Bird, 2020), and experience mild winters and long nesting windows (e.g. ~ 4 month lay date range in northwest Texas: Mullican, 2018), which may make them less vulnerable to mismatch. ...
Preprint
Climate-driven advances in spring can result in phenological mismatch between brood rearing and prey availability and consequently cause decreased productivity in birds. How consequences of mismatch vary across species’ ranges, and how individual behavior can mitigate mismatch effects is less studied. We quantified the relationship between phenological mismatch, productivity, and behavioral adaptations of American kestrels ( Falco sparverius ) across their breeding range in the United States and southern Canada. We obtained phenology and productivity data using nest observations from long term nest box monitoring, remote trail cameras, and community-scientist based programs. We collected data on parental incubation behavior and hatch asynchrony using trail cameras in nest boxes. Kestrels that laid eggs after the start of spring had higher rates of nest failure and fewer nestlings than earlier nesters, and effects of mismatch on productivity were most severe in the Northeast. In contrast, kestrels in the Southwest experienced a more gradual decline in productivity with seasonal mismatch. We attribute the effect of location to the growing season and temporal nesting windows (duration of nesting season). Specifically, resource availability in the Northeast is narrow and highly peaked during the breeding season, potentially resulting in shorter nesting windows. Conversely, resource curves may be more prolonged and dampened in the Southwest, and growing seasons are becoming longer with climate change, potentially resulting in longer nesting windows. We found that the onset of male incubation was negatively associated with lay date. Males from breeding pairs that laid eggs after the start of spring began incubation sooner than males from breeding pairs that laid before the start of spring. Early-onset male incubation was positively associated with hatching asynchrony, creating increased age variation in developing young. In sum, we demonstrate that American kestrels are vulnerable to phenological mismatch, and that this vulnerability varies across space. Northeastern populations could be more vulnerable to mismatch consequences, which may be one factor contributing to declines of kestrels in this region. Also, we demonstrate early onset of incubation as a potential adaptive behavior to advance average hatch date and spread out offspring demands, but it is unknown how impactful this will be in mitigating the fitness consequences of phenology mismatch. Highlights Climate-driven phenological mismatch is a growing conservation concern. We studied phenology and productivity of an avian predator across North America. American kestrels nesting after the start of spring had lower productivity. Later nesting kestrels altered incubation to create hatching asynchrony. Mismatch effects were strongest in the Northeast and may contribute to population declines.
... d Based on a modal clutch size of 5 (Smallwood and Bird 2002), a 2.4-day laying interval (Porter and Wiemeyer 1972), a 30 day incubation period (Bird and Palmer 1988), and a 22-day minimum acceptable fledging age (Steenhof and Peterson 2009). ...
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Studies of nesting success can be valuable in assessing the status of raptor populations, but differing monitoring protocols can present unique challenges when comparing populations of different species across time or geographic areas. We used large datasets from long-term studies of 3 raptor species to compare estimates of apparent nest success (ANS, the ratio of successful to total number of nesting attempts), Mayfield nesting success, and the logistic-exposure model of nest survival. Golden eagles (Aquila chrysaetos), prairie falcons (Falco mexicanus), and American kestrels (F. sparverius) differ in their breeding biology and the methods often used to monitor their reproduction. Mayfield and logistic-exposure models generated similar estimates of nesting success with similar levels of precision. Apparent nest success overestimated nesting success and was particularly sensitive to inclusion of nesting attempts discovered late in the nesting season. Thus, the ANS estimator is inappropriate when exact point estimates are required, especially when most raptor pairs cannot be located before or soon after laying eggs. However, ANS may be sufficient to assess long-term trends of species in which nesting attempts are highly detectable. © 2013 The Wildlife Society.
... Today, this area is primarily utilized for farming, producing rice, soybeans, and wheat. As a result, these fields may provide an excellent habitat for small rodents, the main prey of Red-tailed Hawks (Preston and Beane 2009) and kestrels (Smallwood and Bird 2002). ...
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Although Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius) are common raptors in the U.S.A., their wintering population abundance and distribution has not been studied recently in Arkansas. We assessed the temporal and spatial variation in population abundance of Red-tailed Hawks and American Kestrels over the winter in northeastern Arkansas. We conducted weekly surveys from an automobile in Craighead and Poinsett counties, Arkansas, October 2012–March 2013. Abundance of Red-tailed Hawks (n 5 854 total observations) and American Kestrels (n 5 165 total observations) along the transect increased during winter months. The overall abundance indices were 7.05 Red-tailed Hawks per 10 km (highest ever recorded) and 1.36 American Kestrels per 10 km. We found no significant differences in the utilization of the various cover types (i.e., short rice stubble, soybean stubble, and fallow areas/roadsides) for either species. However, both species differed in their use of perch types (i.e., utility poles, utility crossbeams, utility wires, trees, and other [such as ground, signs, or farming equipment]). Red-tailed Hawks perched on trees and crossbeams significantly more than on other perches. American Kestrels used utility wires as perches significantly more than any of the other perch types. We concluded that northeastern Arkansas is an important wintering area for migrating Red-tailed Hawks and American Kestrels, despite the large-scale agricultural fields present year-round in the landscape.
... Furthermore, we can speculate about the link between this behavior and the availability of prey in the Lesser Antilles island environment. The American Kestrel most commonly captures its prey, mainly small rodents, on the ground using a ''sitand-wait'' technique from a hunting perch or by hoverhunting (Smallwood and Bird 2002). However, on Marie-Galante such terrestrial mammals are represented by rats (Rattus rattus) and mice (Mus musculus) introduced in historical periods (Soubeyran et al. 2011) and whose density is limited on the island. ...
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Here we report the predation on a colony of Lesser naked-backed bat (Pteronotus davyi) by a pair of American Kestrel (Falco sparverius) based on observations over a 16 day period. Kestrels preyed on bats in the evening as they were leaving their roost with two factors controlling hunting efficiency, namely: (1) meteorological conditions, and (2) the time of flock formation. The frequency of occurrence is 93.8% and the success rate is 16.4%. We estimate that bats provide 6.25% of the kestrel's daily food requirement. The case reported here is the first to describe the regular predation of a bat colony by the American Kestrel – a hunting behaviour that has never before been reported for this species This behaviour is interpreted as an example of the trophic adaptation of the American Kestrel to island environments typical of the Lesser Antilles.
... Greater numbers of wintering adult than juvenile Red-tailed Hawks have also been reported by Gates (1972) and by Lish and Burge (1995). A factor that may have influenced our male-biased sex ratio of kestrels is that males have been observed wintering farther north than females, which affects the sex ratio of the species at the northern boundaries of their range (approximately at the northern border of Illinois; Smallwood and Bird 2002). Our abundance values for Red-tailed Hawks were lower than those recorded by Lish and Burge (1995) in Oklahoma (October–March, 378.4 Red-tailed Hawks/1000 km) and by Garner and Bednarz (2000) in Arkansas (December– March, 502 Red-tailed Hawks/1000 km). ...
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INFLUENCIA DE LA LATITUD EN LA ABUNDANCIA INVERNAL DE BUTEO JAMAICENSIS Y FALCO SPARVERIUS EN ILLINOIS Utilizamos cinco años de datos de 18 rutas censadas para determinar la estabilidad temporal de un patrón reportado por primera vez hace 100 años, y reconfirmado hace 50 años, de que la abundancia invernal de Buteo jamaicensis y Falco sparverius disminuye al aumentar la latitud, siendo más elevada en las regiones centrales de Illinos que en las regiones del norte. Voluntarios entrenados llevaron a cabo muestreos (n = 143) mensuales conduciendo por rutas seleccionadas de diciembre a febrero, desde 2004–2005 hasta 2008–2009. Encontramos incrementos significativos en la abundancia de ambas especies desde las regiones del norte hacia las regiones centrales de Illinois. No se evidenciaron efectos significativos del año o del mes en la abundancia de B. jamaicensis (media general = 147.2 individuos de B. jamaicensis/1000 km) y en la abundancia de F. sparverius (media general = 51.1 individuos de F. sparverius/1000 km). Del 78% de los individuos de B. jamaicensis identificados por clase de edad, 10% fueron juveniles y 90% fueron adultos. Del 80% de los individuos de F. sparverius identificados por sexo, 64% fueron machos y 36% fueron hembras. Nuestros hallazgos indican que ha habido una estabilidad temporal de 100 años en el patrón de incremento de la abundancia invernal de ambas especies desde el norte hacia el centro de Illinois, a pesar de cambios substanciales tanto en el hábitat como en las prácticas agrícolas durante los últimos 50 años.
... Throat, chin, malar and auricular feathers were the least affected by aberrant plumage, exhibiting nearly normal malar and other vertical dark stripes on a whitish cheek. The kestrel's eyes, cere, legs and orbital skin were all normal in appearance (Smallwood and Bird 2002). The bird appeared to be in good health and exhibited normal behavior during capture, handling and immediately upon release. ...
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The age of the kestrel was initially thought to be juvenile based on the aligned fault bars in the rectrices which is the pattern consistent with simultaneous growth of feathers that normally occurs in nestlings (Hamerstrom 1967). The fault bars are particularly obvious in this individual's tail due to the lack of pigmentation of the feather adjacent to each fault bar; a phenomenon noted previously (Smallwood 1989). However, the dark subterminal band wider than the other dark barring on the tail is consistent with definitive female kestrel plumage (Pyle 2008). This condition could be explained in the case where all the kestrel's tail feathers were pulled out and, while she was growing the rectrices simultaneously, there was a period of stress or starvation that created fault bars in the same relative location on the tail. Also, there is a feather missing from the left side, possibly r4, perhaps due to damage to the feather follicle during the event in which the kestrel lost its tail. Wild raptors missing feathers has been documented in some North American and Eurasian species (Clark 1988). This aberrant bird appeared to have decreased amounts of eumelanin, the pigment responsible for black, dark brown and dark gray colors. The bird appeared to have normal amounts of phaeomelanins, the pigments associated with tan, reddish browns and some yellow feather coloration (Gill 1995). Our supposition that in some feathers eumelanin was decreased or deficient in this particular kestrel was based on the overall faded dark colors in conjunction with the observation that the flight feathers were excessively worn and frayed and the right distal primary tip (p10) was short due to breakage. Abnormal or lack of eumelanin renders feathers less resistant to abrasion and fracture than normal (Bosner 1995). A study of wild normal and pied New Zealand Fantails (Rhipidura Aberrant plumage in wild birds is not uncommon and can be caused by a variety of conditions: genetic mutations (van Grouw 2013), staining (Nesbitt 1975 and Bales 1909), hybridization (Pyle 2008), environmental contaminants (Bortolotti et al. 2003), diet, age, disease, parasites or injury (Guay et al. 2012). On 23 January 2003, while surveying wintering raptors in south Texas, we captured a female American Kestrel (Falco sparverius) with aberrant plumage (Figs. 1 and 2). The kestrel was captured using a bal-chatri (Berger and Mueller 1959) with a house mouse (Mus musculus domesticus) as a lure. The bird was released at the site immediately after it was measured, photographed and banded with an aluminum butt end USGS-issued band. The capture and release location was 6.62 kilometers north-northwest of Hargill, Hidalgo County, Texas. At first glance, this individual appeared to be a very pale female kestrel with dilute plumage, a condition in which there is a quantitative reduction of melanin with faded but normal feather patterns (van Grouw 2006). Upon closer examination we noticed the normally dark barring on the rufous ground color of the body feathers was an abnormally pale brown to silvery gray color. This aberrant plumage occurred on both the dorsal and ventral aspects. The crown and nape feathers surrounding the normal rufous cap were silvery gray instead of the normal slate bluish-gray color. Throat, chin, malar and auricular feathers were the least affected by aberrant plumage, exhibiting nearly normal malar and other vertical dark stripes on a whitish cheek. The kestrel's eyes, cere, legs and orbital skin were all normal in appearance (Smallwood and Bird 2002). The bird appeared to be in good health and exhibited normal behavior during capture, handling and immediately upon release. CAPTURE OF AN AMERICAN KESTREL WITH DILUTE PLUMAGE
... In response to other potential predators in our study (American Kestrel, chipmunk, and snake), adult Eastern Bluebirds uttered fewer chatter and alarm calls that were shorter in duration. Adult Eastern Bluebirds may perceive American Kestrels and, particularly, eastern chipmunks as less threatening than raccoons because American Kestrels prey primarily on ground-dwelling terrestrial arthropods and small mammals (Smallwood and Bird 2002). Eastern chipmunks occasionally eat bird eggs and nestlings (e.g., Landry 1970, King and DeGraaf 2006), but likely represent less of a threat to 12-19-day-old nestling bluebirds than to eggs or smaller nestlings. ...
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ABSTRACT.—The alarm calls of some birds are functionally referential and may provide nestlings with information about the threat posed by potential predators. However, few investigators have examined the responses of nestlings in cavity nests to the anti-predator vocalizations of adults. Our objectives were to examine (1) the vocal responses of cavity-nesting adult Eastern Bluebirds (Sialia sialis) to different predators, and (2) the behavioral responses of nestlings to those vocalizations. From April–July 2013, pairs of Eastern Bluebirds were exposed to mounts or models of four potential nest predators, including a raccoon (Procyon lotor), eastern chipmunk (Tamias striatus), American Kestrel (Falco sparverius), and black rat snake (Pantherophis obsoletus), plus a control (Mourning Dove, Zenaida macroura). During 3-min trials, mounts or models were placed adjacent to nest boxes with 12–19-day-old nestlings. Adult vocalizations were recorded and the behavior of nestlings simultaneously recorded with a camcorder. Adult bluebirds (n527 pairs) uttered longer-duration alarm and chatter calls at significantly higher rates in response to the raccoon, and nestlings responded more often (23 of 39 trials [59%], excluding nine control trials) when adult bluebirds uttered chatter and alarm calls at higher rates. Nestling responses included crouching (21 trials), climbing the walls of the nest box (one trial), and fledging (one trial). Crouching may reduce the risk of predation by large predators unable to enter a nest cavity, but able to reach into it. In contrast, premature fledging when a predator is nearby would likely increase the risk of mortality. Adult Eastern Bluebirds do not produce predator-specific vocalizations, but call characteristics and call rates appear to provide nestlings with information about the presence of potential predators.
... Broad-winged Hawks and Swainson's Hawks have a much later migration termination date during fall but migrate much longer distances (Haines et al. 2003, Kochert et al. 2011). In addition to total migration distance, gender differences in migration initiation dates have also been documented in raptors (Stotz and Goodrich 1989, Smallwood and Bird 2002, Goodrich and Smith 2008. We did not document any substantial differences in migration patterns in the hawks that we tracked based on gender, but our sample size prevents any strong conclusions on the role of gender on migration initiation and termination dates for Red-tailed Hawks. ...
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While a common species throughout most of the United States, little is known on the migration habits of Red-tailed Hawks (Buteo jamaicensis). From 1999-2002, we tracked 16 adult Red-tailed Hawks from their breeding grounds in northwest Wyoming using Argos PTT transmitters. Our objectives were to identify dates and duration of migratory movements, stopover sites, and identify migration routes and wintering areas. We found the mean migration initiation date from the breeding area was 13 October, mean fall migration duration including stopovers was 23.3 days, mean distance of fall migration was 2489.6 km, and mean end date of fall migration was 5 November. Wintering locations were in Mexico and ranged from the southern Mexican state of Chiapas north to Sonora and Chihuahua. The mean number of days spent on the wintering grounds by tracked hawks was 133.1. The mean departure date from wintering grounds to breeding areas was 17 March, mean spring migration duration including stopovers was 22.1 days, mean end date of spring migration was 8 April, and mean distance of spring migration was 2 490.3 km. Most birds made stopovers during both fall and spring migration which varied in location and duration. Using satellite telemetry, we identified wintering locations of Red-tailed Hawks breeding in northwest Wyoming and confirmed a leapfrog migration pattern with no concentrated migration routes from the breeding area to non-breeding areas.
... While the decline of Blue Jays was relatively small, the remaining five birds experienced dramatic declines. Pesticides, in particular DDT, have been implicated in the decline of Loggerhead Shrikes (Pruitt 2000) and American Kestrels (Smallwood and Bird 2002). In Illinois, Herkert (2004) found that 90% of the shrike egg samples in 1971-72 had DDT (or its derivatives), while in 1995 only 11% of eggs contained DDT. ...
... Because populations of American Kestrels may be limited by availability of nest sites (Cade 1982, Smallwood andBird 2002), some authors have suggested that a loss of nest sites might be contributing to population declines (Sullivan andWood 2005, Smallwood andCollopy 2009). Under the assumption that nest-site limitation constrains kestrel populations, professional (e.g., Smallwood et al. 2009b) and citizen science (CJW McClure pers obs) programs are installing artificial breeding sites, in part, to increase nest site availability and thereby slow or reverse population declines. ...
Article
Despite common use, the efficacy of artificial breeding sites (e.g., nest boxes, bat houses, artificial burrows) as tools for monitoring and managing animals depends on the demography of target populations and availability of natural sites. Yet, the conditions enabling artificial breeding sites to be useful or informative have yet to be articulated. We use a stochastic simulation model to determine situations where artificial breeding sites are either useful or disadvantageous for monitoring and managing animals. Artificial breeding sites are a convenient tool for monitoring animals and therefore occupancy of artificial breeding sites is often used as an index of population levels. However, systematic changes in availability of sites that are not monitored might induce trends in occupancy of monitored sites-a situation rarely considered by monitoring programs. We therefore examine how systematic changes in unmonitored sites could bias inference from trends in the occupancy of monitored sites. Our model also allows us to examine effects on population levels if artificial breeding sites either increase or decrease population vital rates (survival and fecundity). We demonstrate that trends in occupancy of monitored sites are misleading if the number of unmonitored sites changes over time. Further, breeding site fidelity can cause an initial lag in occupancy of newly installed sites that could be misinterpreted as an increasing population, even when the population has been continuously declining. Importantly, provisioning of artificial breeding sites only benefits populations if breeding sites are limiting or if artificial sites increase vital rates. There are many situations where installation of artificial breeding sites, and their use in monitoring, can have unintended consequences. Managers should therefore not assume that provision of artificial breeding sites will necessarily benefit populations. Further, trends in occupancy of artificial breeding sites should be interpreted in light of potential changes in the availability of unmonitored sites and the potential of lags in occupancy owing to site fidelity. This article is protected by copyright. All rights reserved.
... American kestrels (Falco sparverius) are small falcons that feed primarily on small mammals, and insects, and occasionally on birds and reptiles (Smallwood & Bird 2002). Kestrels are secondary cavity nesters and use a variety of land cover types that include shrub and grasslands and agricultural and suburban areas (Bird & Palmer 1988). ...
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Warming temperatures cause temporal changes in growing seasons and prey abundance that drive earlier breeding by birds, especially dietary specialists within homogeneous habitat. Less is known about how generalists respond to climate-associated shifts in growing seasons or prey phenology, which may occur at different rates across land cover types. We studied whether breeding phenology of a generalist predator, the American kestrel (Falco sparverius), was associated with shifts in growing seasons and, presumably, prey abundance, in a mosaic of non-irrigated shrub/grasslands and irrigated crops/pastures. We examined the relationship between remotely-sensed normalized difference vegetation index (NDVI) and abundance of small mammals that, with insects, constitute approximately 93% of kestrel diet biomass. We used NDVI to estimate the start of the growing season (SoGS) in irrigated and non-irrigated lands from 1992 to 2015 and tested whether either estimate of annual SoGS predicted the timing of kestrel nesting. Finally, we examined relationships among irrigated SoGS, weather and crop planting. NDVI was a useful proxy for kestrel prey because it predicted small mammal abundance and past studies showed that NDVI predicts insect abundance. NDVI-estimated SoGS advanced significantly in irrigated lands (β = -1·09 ± 0·30 SE) but not in non-irrigated lands (β = -0·57 ± 0·53). Average date of kestrel nesting advanced 15 days in the past 24 years and was positively associated with the SoGS in irrigated lands, but not the SoGS in non-irrigated lands. Advanced SoGS in irrigated lands was related to earlier planting of crops after relatively warm winters, which were more common in recent years. Despite different patterns of SoGS change between land cover types, kestrel nesting phenology shifted with earlier prey availability in irrigated lands. Kestrels may preferentially track prey in irrigated lands over non-irrigated lands because of higher quality prey on irrigated lands, or earlier prey abundance may release former constraints on other selective pressures to breed early, such as seasonal declines in fecundity or competition for high-quality mates. This is one of the first examples of an association between human adaptation to climate change and shifts in breeding phenology of wildlife.
... Where the Snowy Owl occurs in winter in Ontario, it prefers open places such as fields, prairies, marshes, coasts, and the shorelines of lakes and large rivers. This bird will perch on the ground, fence posts, straw stacks, trees, radio towers and buildings (Godfrey 1986 (Smallwood and Bird 2002). ...
... American Kestrels (Falco sparverius) are small, cavity-nesting falcons that are widespread across North and South America. Kestrels readily use nest boxes for breeding and nest box programs are common throughout their range (Smallwood and Bird 2002). In response to observed declines in populations across much of North America, McClure et al. (2017b) recently called for research into the nonbreeding ecology of American Kestrels. ...
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Nest boxes are posted to provide breeding sites for cavity-nesting birds but less is known about their function in the nonbreeding season, when nest boxes may become important roost sites. In winter months, we surveyed 79 nest boxes before dawn for roosting American Kestrels (Falco sparverius) and other cavity-nesting birds in southwestern Idaho and we reviewed camera recordings from the entire nonbreeding season at a nest box within the study site to better understand nest box use in the nonbreeding season. During surveys we found seven American Kestrels roosting in six nest boxes, Northern Flickers (Colaptes auratus) in 16 nest boxes and a European Starling (Sturnus vulgaris) in one nest box. Video recordings revealed inter- and intra-specific conflicts within the nest box as well as a positive relationship between the length of night and the time spent roosting in the box. These results suggest that cavity-nesting birds in our study area are likely to seek out and compete for nest boxes to use as roost sites in the nonbreeding season and the effects of nest boxes on the nonbreeding season ecology of birds should be considered.
... Habitat edges and ecotones are important to Northern Shrikes (Atkinson 1993). For example, agricultural land comprised a large portion of the "Chino" shrike's winter home range in 2008-2009 at 43.35% (Table 2), however the bird was not found in the middle of the agricultural fields, but invariably occupied edges where there are perch locations (Figure 2), in the same manner that American Kestrels, Falco sparverius, use road edges surrounding agricultural land with perches such as utility wires or trees (Smallwood and Bird 2002). A large portion of the core range, and apparently highly important to this individual, consisted of native warm season grasses and early successional shrub-scrub (four-year average 58% and 35%, respectively). ...
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Observations were made of a single adult Northern Shrike (Lanius borealis) over a four-year period during the winters of 2007–2008 to 2011–2012 on the Eastern Shore of Maryland. A new record early arrival date of 13 October and a record late last occurrence date of 16 April were established for the state. Average annual residence time was 155 days ±13.9 SE. Average home range size was 71.7 ha ±23.1 SE (177.1 ac ±57.1 SE) using the minimum convex polygon method and 69.1 ha ±17.7 SE (170.5 ac ±43.7 SE ) using the kernel density estimate for 95% percent volume contours. Average core home range or 50% percent volume contours was 13.7 ha ±5.49 SE (33.9 ac ±13.6 SE). Each winter’s home range was comprised of multiple habitat types, but native grasslands and early successional shrub-scrub habitat annually dominated the core home range.
... Destruction and alteration of breeding habitat is a potential threat to many species and the American Kestrel is no exception (Sullivan and Wood 2005, Farmer et al. 2008, Smallwood et al. 2009a, Wommack et al. 2014, Bolgiano et al. 2015. American Kestrels are secondary cavity nesters (Smallwood and Bird 2002) and several studies have demonstrated population increases after the installation of nest boxes (Nagy 1963, Hamerstrom et al. 1973, Stahlecker and Griese 1979, Bloom and Hawks 1983, Wilmers 1983, Toland and Elder 1987, Smallwood and Collopy 2009, leading some to suggest that a lack of nest cavities might be causing population declines (Sullivan and Wood 2005). However, that occupancy of nest boxes is declining at several locations across North America (Smallwood et al. 2009a) suggests that those populations are not limited by nest sites and therefore that a loss of nest cavities is not a cause of decline in those areas (McClure et al. 2017)-i.e., previously productive breeding sites should not be vacant if nest sites are limiting. ...
... [Traducción del equipo editorial] 1 Email address: cartergcrouch@gmail.com American Kestrels (Falco sparverius) are the most common and widespread North American falcon (Smallwood and Bird 2002). Researchers have several alternatives available to uniquely mark individuals, and there are important factors to consider when choosing a marker type (Varland et al. 2007). ...
Article
We compared two color-marking techniques, celluloid color leg bands and colored dye on the feathers, for individual identification of American Kestrels (Falco sparverius). We trapped and color-marked 65 kestrels in October through December of 2014 and 2015. We searched for kestrels once a week with binoculars and a spotting scope and each time, recorded how kestrels were marked, either by bands, dye, or both. We confirmed that seven of the 195 color bands were lost during the study. The longest time that dye was still visible was 149 d after marking. We saw color bands from a maximum distance of 245 m and color dye from a maximum distance of 428 m. Of kestrels we were able to identify at least 10 times (n = 39) within the season that markings were applied, we saw only dye 17.3% of the time and only bands 19.4% of the time. We saw both markers (dye and at least one band) 63.3% of the time. Both methods can be used for successful identification of wintering kestrels, but a combination of the two techniques can increase the chance of seeing an identifiable mark. Color bands are long-term markers and allow identification of kestrels whose dye has faded or those that return in following years. Color dye makes it easier to identify kestrels that are difficult to approach, as well as those with territories extending away from accessible roadways.
... The American Kestrel (Falco sparverius) is an obligate cavity nester that typically nests in tree cavities excavated by woodpeckers, hollows in large tree branches, and nest boxes (Smallwood and Bird 2002). Kestrels also make use of other anthropogenic structures for nesting, including nooks and crannies in buildings, chimneys, fence posts (Bird and Palmer 1988), and hollow metal structures in electrical transmission towers (Maney andParrish 2007, Beasley andParrish 2009). ...
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We report on the nesting of Southeastern American Kestrels (Falco sparverius paulus) in nonnative Monk Parakeet (Myiopsitta monachus) nests in Florida, USA. Two kestrel pairs nested within parakeet stick nests located on top of steel support structures at electric utility substations in Pasco County, Florida. Kestrels fledged young at both sites. The Monk Parakeet's ability to exploit anthropogenic habitats may facilitate the use of these areas by nest-site-limited species such as the Southeastern American Kestrel.
... The most commonly detected raptor, American kestrel (Falco sparverius), was also the least likely to have direct predation effects on sage-grouse. Kestrels mainly prey on invertebrates, small mammals, and reptiles (Smallwood and Bird 2002). Red-tailed hawk (Buteo jamaicensis) and golden eagles were detected at all sites but at insufficient levels to obtain density estimates from transect data. ...
... Destruction and alteration of breeding habitat is a potential threat to many species and the American Kestrel is no exception (Sullivan and Wood 2005, Farmer et al. 2008, Smallwood et al. 2009a, Wommack et al. 2014, Bolgiano et al. 2015. American Kestrels are secondary cavity nesters (Smallwood and Bird 2002) and several studies have demonstrated population increases after the installation of nest boxes (Nagy 1963, Hamerstrom et al. 1973, Stahlecker and Griese 1979, Bloom and Hawks 1983, Wilmers 1983, Toland and Elder 1987, Smallwood and Collopy 2009, leading some to suggest that a lack of nest cavities might be causing population declines (Sullivan and Wood 2005). However, that occupancy of nest boxes is declining at several locations across North America (Smallwood et al. 2009a) suggests that those populations are not limited by nest sites and therefore that a loss of nest cavities is not a cause of decline in those areas (McClure et al. 2017)-i.e., previously productive breeding sites should not be vacant if nest sites are limiting. ...
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Most raptor populations are declining and nearly a fifth are threatened with extinction; thus there is a need to increase collaboration to ensure efficient and effective research, management, and conservation. Here, we introduce the Global Raptor Impact Network (GRIN; www.globalraptors.org), a tool to enhance collaboration and conservation impact of the raptor research community. We provide an overview of the history and current state of GRIN, including plans for expansion. Predecessors to GRIN include The African Raptor DataBank, which was launched in 2012 to ascertain the conservation status of raptors across Africa; and the Global Raptor Information Network, which was launched in the late 1990s as a website to provide information regarding diurnal raptors and facilitate communication among researchers. GRIN expands the data collection and storage capabilities of the African Raptor DataBank to a global scale via mobile application. We have implemented data-sharing rules to ensure the safety of sensitive species, and users of the GRIN mobile app can designate their records as confidential. GRIN staff and partners are developing analyses of species' population trends and geographic distributions to aid in conservation assessments. GRIN is also developing systematic reviews, detailed bibliographies, and online accounts that will summarize the state of knowledge for each raptor species. We hope that GRIN will benefit the entire raptor research community and aid in the collaboration necessary to help raptor populations thrive in the Anthropocene.
... Similarly, research on the American Kestrel (Falco sparverius) has shown declining counts at many migration sites, shorter migration distances, and increasing counts at some wintering areas over a similar period (Farmer and Smith 2009, Heath et al. 2012, Paprocki et al. 2014. Comparable to the Red-tailed Hawk, the Common Buzzard and American Kestrel exhibit population-specific migratory propensity, with northern breeders being migratory and southern breeders being more sedentary (Smallwood andBird 2002, Martin et al. 2014). Given the life-history similarities and our results, we propose that a similar change is likely occurring in Red-tailed Hawks in North America. ...
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An increasing body of scientific evidence supports the idea that many avian species are changing their migratory behavior as a result of climate change, land-use change, or both. We assessed Red-tailed Hawk (Buteo jamaicensis) population trends in 2 parts of the annual cycle (fall migration and winter) to better understand regional population trends and their relationship to changes in migration. We conducted 10 yr, 20 yr, and 30 yr trend analyses using pan-North American standardized fall migration counts and Christmas Bird Counts. We quantitatively compared trends in seasonal counts by latitude within the eastern and western migratory flyways. Our combined analysis of migration and wintering count data revealed flyway-specific patterns in count trends suggesting that Red-tailed Hawks are undergoing substantial changes in both migratory behavior and population size. Decreasing Red-tailed Hawk wintering and migration counts in southern regions and increasing winter counts in northern regions were consistent with other observations indicating changes in migratory strategy; an increasing number of Red-tailed Hawks do not migrate, or migrate shorter distances than they did in the past. Further, Red-tailed Hawk populations have been stable or increasing across much of North America. However, we found strong negative count trends at the northernmost migration sites on the eastern flyway, suggesting possible breeding-population declines in the central and eastern Canadian provinces. Our findings demonstrate the benefit of using appropriate data from multiple seasons of the annual cycle to provide insight into shifting avian migration strategies and population change.
... Birds were sexed based on the plumage coloration, as they are sexually dimorphic (Dunn 2017). The American kestrel is a small-sized raptor (average weight = 80-165 g, total length = 22-31 cm), and females are heavier (129.1 g average weight) than males (110.7 g) (Bohall-Wood and Collopy 1987; Layne and Smith 1992;Smallwood and Bird 2002). Additional differences in weight can also be found during the post-breeding season, when resident kestrels coexist with larger kestrels from the USA and Canada that migrate to the Baja California peninsula (Moore and Bond 1946). ...
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Raptors as top predators have been used as effective sentinels of environmental stressors in agricultural areas worldwide. Pollutants in agricultural areas have negative effects on top predator populations. Biomarkers such as erythrocyte nuclear abnormalities have been used as an effective measure of genotoxicity caused by exposure—particularly short-term exposure—to pollutants. We took blood samples from 54 wild specimens of American kestrel (Falco sparverius) captured in an agricultural area in Valle de Santo Domingo, Baja California Sur, Mexico in the autumns of 2018 and 2019 (n = 25) and the winters of 2019 and 2020 (n = 29). We prepared and examined blood smears to look for erythrocyte abnormalities as a means to evaluate genotoxicity. The number of abnormality types and the total frequency of abnormalities (MNs and NAs: notched, symmetrically or asymmetrically constricted, displaced, or indented nuclei) per 10,000 erythrocytes were calculated for all the specimens. We found a high frequency of abnormalities in numerous individuals, similar to those found in raptors from highly polluted areas. The best-fit generalized linear model for the number of abnormality types included season-of-the-year as the main significant predictor; the model for the total frequency of abnormalities included season and wing chord, an indicator of body size and health condition, as significant predictors. MNs frequencies were significantly related to season; NAs frequencies were related to season, wing chord length, and coverage of native vegetation around the area where the birds were captured. Abnormalities observed in the autumn closely coincide with the time when agrochemicals are applied in the area, mainly after the rains and during hot spells in late summer and early autumn. Small-sized kestrels showed higher frequencies of NAs, with an additional impact if native vegetation had been cleared for agriculture; this suggests both that resident birds are more exposed, and the observed genotoxicity has a local origin. These results, together with the ecological and physiological characteristics of the American kestrel suggest that this charismatic and widely distributed species might constitute a suitable biomonitor of genotoxicity in rural landscapes.
... In addition, kestrels provide ecosystem services in some fruit-producing regions by reducing the abundance of fruit-eating birds . Despite being the most abundant and widespread North American falcon (Smallwood and Bird 2002), evidence indicates that the kestrel has experienced population declines, particularly in the eastern part of the continent (Farmer et al. 2008, Farmer and Smith 2009, Smallwood et al. 2009a, Sauer et al. 2013. Although kestrels primarily feed on invertebrates, their diet varies from place to place and year to year; they sometimes take mammals, birds, and reptiles approaching their own body size Bird 2002, Shave 2017). ...
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We assessed the conservation status of 20 species of North American birds of prey by examining historical and recent estimates of trends in counts of raptors at migration watchsites. We compared these trend estimates with trends in Breeding Bird Surveys (BBSs), Christmas Bird Counts (CBCs) (terms in italics are defi ned in the book's glossary), and other available population indexes for areas believed to be either the origin or destination of migrants passing watchsites in each of three geographic regions. Long-term trend estimates indicated mostly increasing migration counts for nine species, mostly decreasing trends for fi ve species, and mixed trends for six species. In the most recent decade, trends were geographically mixed for most species, with annual declines beginning in the late 1990s for many species in the West. We found evidence of widespread declines in populations of American Kestrels ( Falco sparverius), and long-term increases for Bald Eagles ( Haliaeetus leucocephalus), Swainson's Hawks ( Buteo swainsoni), Merlins ( F. columbarius), and Peregrine Falcons ( F. peregrinus). Species with geographically mixed trends included the Broad-winged Hawk ( B. platypterus), Red-shouldered Hawk ( B. lineatus), Red-tailed Hawk ( B. jamaicensis), Rough-legged Hawk (B. lagopus), and Golden Eagle ( Aquila chrysaetos). Considered together, evidence from migration counts, BBSs, and CBCs suggests changes in migratory activity, rather than popula- tion changes, as the cause of decreasing migration counts of several species since 1974.
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ACKNOWLEDGMENTS This study was conducted under the auspices ofthe Bats and Wind Energy Cooperative. We wish to thank the American Wind Energy Association (AWEA), Bat Conservation International (BCI), the National Renewable Energy Laboratory-Department of Energy (NREL), and the U.S. Fish and Wildlife Service (USFWS) for partnering to form the Bats and Wind Energy Cooperative (BWEC). Tom Gray (AWEA), Alex Hoar (USFWS), Bob Thresher (NREL), and Merlin Tuttle (BCI) provided oversight for the BWECthe project.
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Raptor conservation programs should be based on knowledge of the birds’ ecology in both natural and urban habitats, justifying the inclusion of ecological studies in suburban zones into regional planning initiatives. The objectives of this study were (a) to determine the use by diurnal raptors of the habitat in a suburban area of a city in southern Chile, and (b) to characterize the different zones into five types of environment, and assess their raptor diversity for consideration in territorial planning. Acoustic surveys were conducted in auditory stations in addition to observations from fixed transects and trails. From a total of 161.39 hours of census, we obtained 664 sightings corresponding to ten species of diurnal raptors. The richest environment was dense forest (eight species), followed by grassland (six species), native forest regeneration (five species), shrubs (four species) and exotic tree plantations (three species). We discuss the relationship between the richness of diurnal raptors, the types of environment in the study area, and the spatial location of the sites, as well as the implications for territorial planning to support the conservation of birds of prey in the suburban zone studied.
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Falco sparverius (American Kestrel) and Lanius ludovicianus (Loggerhead Shrike) have undergone major population declines, which may be partially due to habitat changes on their wintering grounds. The objectives of this study were to compare quantitative habitat metrics and landcover data at sites used by American Kestrels and Loggerhead Shrikes during the winter. We conducted this study by observing individuals of both species along private and public roads across 8 counties in South Texas and recording GPS coordinates and various habitat characteristics at each location. We calculated woody canopy cover by digitizing all woody cover within 100 m of the sighting locations and at random points, and obtained landcover data from the National Land Cover Database (NLCD) for 2001 and 2011. Female American Kestrels were associated with shorter herbaceous height (median = 7.4 cm) than male American Kestrels (16.4 cm) or Loggerhead Shrikes (13.6 cm). Woody canopy cover was lower around sites used by female American Kestrels (q0.9 = 1.9%), compared to sites used by male American Kestrels (q0.9 = 17.8%), Loggerhead Shrikes (q0.9 = 21.3%), or at random points (q0.9 = 51.6%). Although cultivated crops were the most common cover type within 100-m radius buffers of each species group, this cover type was more abundant (73.2% ± 1.5) in sites used by female American Kestrels than sites used by male American Kestrels (47.7% ± 4.1) or Loggerhead Shrikes (41.1% ± 2.7). In contrast, sites used by female American Kestrel had lower amounts of pasture/hay, grassland/herbaceous, and shrub/scrub types compared to those used by male American Kestrels or Loggerhead Shrikes. Two of the most important cover classes for American Kestrels and Loggerhead Shrikes, cultivated crops and pasture/hay, still comprised 26.0% (481,882 ha) and 22.3% (413,396 ha) of these 8 South Texas counties in 2011, but had decreased by 0.77% and 0.84% since 2001. Medium- and high-intensity development has increased, for a total of 3360 ha (15.49% change), over the same timeframe. Slowing the loss of these favorable open-cover habitat types should be a priority for the conservation of American Kestrels and Loggerhead Shrikes in South Texas.
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The populations of many species of raptors that forage in agroecosystems have declined as agriculture has intensified. Cover crops are a recent trend in areas of intensive row-crop agriculture in the Midwestern United States that could positively affect raptors by increasing the abundance and distribution of raptor prey. We assessed the habitat use of two raptors, American Kestrel (Falco sparverius) and Red-tailed Hawk (Buteo jamaicensis), and tested for use of areas near cover-cropped fields. We conducted 1184 km of roadside transects in 2018 and 2019 in west-central Indiana and recorded 191 detections of our focal species. We constructed resource selection functions within a use-availability design to evaluate raptor habitat use with a series of weighted logistic regression models. For each species, we fitted models at two scales (transect and landscape) and with two definitions of available points (completely random and random subject to perch constraints). American Kestrels were strongly associated with cover-cropped agricultural fields. Red-tailed Hawks were strongly associated with woodlots. Scale did not greatly affect the inclusion of habitat variables into top models for either species. Random models identified potential perch sites, whereas constrained random models identified more subtle habitat preferences not included in the random models. For American Kestrels, constrained models revealed reduced use of woodland perches and increased use of perches near cover-cropped and conventional agricultural fields. For Red-tailed Hawks, constrained models revealed habitat associations, particularly reduced use of utility lines and human development, that were absent or de-emphasized in random models. Modeling resource selection with constrained random availability will work best for well-studied species with discrete, easily mapped habitat features. If damage to commodity crops by rodents in cover-cropped fields is a concern, raptor management should focus on kestrels and could include erection of artificial perches, nest boxes, and enhancement of permanent herbaceous habitats for hunting.
Chapter
This chapter provides a brief overview of how natural gradients (e.g., latitude, altitude, and landscape gradients) affect host–parasite interactions involving blood parasites in wildlife and how biotic and abiotic factors act as disruptors. These gradients have a direct impact on prevalence, parasitemia, and the observed relationships between parasites and hosts. In the tropical zone, altitudinal gradients imitate the behavior of the latitudinal gradient, since low temperatures are common at both higher altitudes and higher latitudes. Temperature is one of the determining factors of the diversity of vectors, hosts, and vegetation that affect parasite transmission cycles. Furthermore, within landscapes, there may be many types of elements producing gradients. For instance, increasing distance from water sources, anthropogenic degradation, and even sequential stages of succession and interspersion of vegetation communities would affect host–parasite–vector interactions. However, such effects do not always operate in the same direction because responses are context sensitive. We also discuss the importance of an integrative diagnosis, using microscopic and molecular approaches, which allow better approximations and analyses at the parasite species level, thus producing stronger conclusions. The same detail is recommended for studies on the hematophagous fauna of potential vectors. The life cycle of different parasite species has its own set of characteristics, and it corresponds to the researchers to unravel the puzzle and to avoid unwarranted generalizations.
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Nesting biology of birds from southeastern Minas Gerais, Brazil. We report several aspects of the nesting biology, with emphasis on nest and egg characteristics, nesting period, occurrence of brood patches, and reproductive behavior of birds nesting mostly in forests of Belo Horizonte, Nova Lima and Ibirite counties, state of Minas Gerais, Brazil. We studied 108 nests of 34 species during the reproductive seasons of 1995 through 2000, which characteristics are described and compared with the literature.
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