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At least 37 records · Page 2Linked to original sources
USGS2025

Prairie Falcon (Falco mexicanus) abundance in a National Conservation Area in Idaho has increased since the 1970s–1990s

The Morley Nelson Snake River Birds of Prey National Conservation Area (NCA), in southwestern Idaho, USA supports a large population of breeding Prairie Falcons ( Falco mexicanus ). Abundance of Prairie Falcons in the NCA was previously monitored in 1976–1978 and 1990–1994. That research indicated maximum counts for each period in 1976 and 1992 and a possible population decline across that time span. We assessed the abundance and nesting success of Prairie Falcons in the NCA in 2002–2003 and 2019–2021, and we compared results to data from before 2000 to assess possible population change. Number of nesting pairs increased over 45 years from peak counts of 206, 193, and 217 in the 1970s, 1990s, and early 2000s, respectively, to 257 in 2021. Increases were not concentrated in one region, but widely distributed across the study area. Rates of nesting success in 2002–2003 and 2019–2021 averaged 57 ± 11.8% (SD) at 49.8 ± 3.3 nests observed each year and did not differ from pre-2000 rates. Finally, our analysis showed that in all 10 years in which a full census was conducted, a sampling approach to surveys would have been effective at estimating the number of falcons nesting within the NCA. Prairie Falcons are of conservation concern because of possible population declines in parts of their range. These results illustrate an area with apparently increasing numbers of this important species and highlight the importance of long-term surveys for tracking population fluctuations and the value of a national conservation area for providing raptor breeding habitat.

Idaho↗
USGS2017

Demographic consequences of nest box use for Red-footed Falcons Falco vespertinus in Central Asia

Nest box programs are frequently implemented for the conservation of cavity-nesting birds, but their effectiveness is rarely evaluated in comparison to birds not using nest boxes. In the European Palearctic, Red-footed Falcon Falco vespertinus populations are both of high conservation concern and are strongly associated with nest box programs in heavily managed landscapes. We used a 21-year monitoring dataset collected on 753 nesting attempts by Red-footed Falcons in unmanaged natural or semi-natural habitats to provide basic information on this poorly known species; to evaluate long-term demographic trends; and to evaluate response of demographic parameters of Red-footed Falcons to environmental factors including use of nest boxes. We observed significant differences among years in laying date, offspring loss, and numbers of fledglings produced, but not in egg production. Of these four parameters, offspring loss and, to a lesser extent, number of fledglings exhibited directional trends over time. Variation in laying date and in numbers of eggs were not well explained by any one model, but instead by combinations of models, each with informative terms for nest type. Nevertheless, laying in nest boxes occurred 2.10 ± 0.70 days earlier than in natural nests. In contrast, variation in both offspring loss and numbers of fledglings produced were fairly well explained by a single model including terms for nest type, nest location, and an interaction between the two parameters (65% and 81% model weights respectively), with highest offspring loss in nest boxes on forest edges. Because, for other species, earlier laying dates are associated with more fit individuals, this interaction highlighted a possible ecological trap, whereby birds using nest boxes on forest edges lay eggs earlier but suffer greater offspring loss and produce lower numbers of fledglings than do those in other nesting settings. If nest boxes increase offspring loss for Red-footed Falcons in heavily managed landscapes where populations are at greater risk, or for the many other species of rare or endangered birds supported by nest box programs, these processes could have important demographic and conservation consequences.

Ibis↗
USGS2017

Intraspecific evolutionary relationships among peregrine falcons in western North American high latitudes

Subspecies relationships within the peregrine falcon ( Falco peregrinus ) have been long debated because of the polytypic nature of melanin-based plumage characteristics used in subspecies designations and potential differentiation of local subpopulations due to philopatry. In North America, understanding the evolutionary relationships among subspecies may have been further complicated by the introduction of captive bred peregrines originating from non-native stock, as part of recovery efforts associated with mid 20 th century population declines resulting from organochloride pollution. Alaska hosts all three nominal subspecies of North American peregrine falcons– F . p . tundrius , anatum , and pealei –for which distributions in Alaska are broadly associated with nesting locales within Arctic, boreal, and south coastal maritime habitats, respectively. Unlike elsewhere, populations of peregrine falcon in Alaska were not augmented by captive-bred birds during the late 20 th century recovery efforts. Population genetic differentiation analyses of peregrine populations in Alaska, based on sequence data from the mitochondrial DNA control region and fragment data from microsatellite loci, failed to uncover genetic distinction between populations of peregrines occupying Arctic and boreal Alaskan locales. However, the maritime subspecies, pealei , was genetically differentiated from Arctic and boreal populations, and substructured into eastern and western populations. Levels of interpopulational gene flow between anatum and tundrius were generally higher than between pealei and either anatum or tundrius . Estimates based on both marker types revealed gene flow between augmented Canadian populations and unaugmented Alaskan populations. While we make no attempt at formal taxonomic revision, our data suggest that peregrine falcons occupying habitats in Alaska and the North Pacific coast of North America belong to two distinct regional groupings–a coastal grouping ( pealei ) and a boreal/Arctic grouping (currently anatum and tundrius )–each comprised of discrete populations that are variously intra-regionally connected.

Alaska↗
USGS2005

Spacing and physical habitat selection patterns by peregrine falcons in central West Greenland

We examined nest-site spacing and selection of nesting cliffs by Peregrine Falcons ( Falco peregrinus ) in central West Greenland. Our sample included 67 nesting cliffs that were occupied at least once between 1972 and 1999 and 38 cliffs with no known history of Peregrine Falcon occupancy. We measured 29 eyrie, cliff, and topographical features at each occupied nesting cliff and unused cliff in 1998a??1999 and used them to model the probability of peregrines occupying a cliff for a breeding attempt. Nearest-neighbor distance was significantly greater than both nearest-cliff distance and nearest-occupied distance (the distance between an occupied cliff and one occupied at least once, 1972a??1999). Thus, spacing among occupied cliffs was probably the most important factor limiting nesting-cliff availability, and, ultimately, peregrine nesting densities. Although some unused cliffs were unavailable in a given year because of peregrine spacing behavior, physical characteristics apparently made some cliffs unsuitable, regardless of availability. We confirmed the importance of several features common to descriptions of peregrine nesting habitat and found that peregrines occupied tall nesting cliffs with open views. They chose nesting cliffs with eyrie ledges that provided a moderate degree of overhang protection and that were inaccessible to ground predators. Overall, we concluded that certain features of a cliff were important in determining its suitability as a nest site, but within a given breeding season there also must be sufficient spacing between neighboring falcon pairs. Our habitat model and information on spacing requirements may be applicable to other areas of Greenland and the Arctic, and can be used to test the generalities about features of Peregrine Falcon nesting cliffs throughout the species' widespread distribution.

Kangerlussuaq↗
USGS2007

Further assessment of environmental contaminants in avian prey of the peregrine falcon in big bend National Park, Texas

A small resident population of peregrine falcons (Falco peregrinus anatum) in the Big Bend region of Texas has suffered reproductive failures since 1990. To continue our assessment of the effects of environmental contaminants on the peregrine falcon, we collected representative avian prey species during 2001 at Mariscal Canyon, Big Bend National Park. The avian carcasses were analyzed for inorganic and organochlorine contaminants. Concentrations of Se and Hg were present at high levels (up to 11 and 2.2 ??g/g dry weight, respectively) in some avian prey and could be implicated in reproductive failures of the peregrine falcon in Big Bend National Park. All other inorganic elements were below concentrations known to affect reproduction or to be associated with other deleterious effects in birds. Of all the organochlorines analyzed, only DDE and total PCBs were present above detection limits in all species, although at low concentrations. Our study provides further support to the hypothesis that contaminants in potential avian prey of the peregrine falcon in the Big Bend region are implicated in the productivity failures observed in this species since 1990.

Southwestern Naturalist↗
USGS1998

Routes and travel rates of migrating Peregrine Falcons Falco peregrinus and Swainson's Hawks Buteo swainsoni in the Western Hemisphere

We describe and compare the migration routes, length of migration, and duration of migration of Peregrine Falcons Falco peregrinus tundrius and Swainson's Hawks Buteo swainsoni in the Western Hemisphere. We radio tracked migrants using the Argos satellite system. Our initial samples were 34 Swainson's Hawks from representative areas of their breeding range, and 61 Peregrine Falcons captured at nest sites across the North American boreal forest and low Arctic or on the migration routes along the mid-Atlantic and Gulf of Mexico coasts. The average distance of migration for Peregrines was 8,624 km southward, and 8,247 km northward. Peregrines travelled at an average rate of 172 km/d southward and 198 km/d going north. Peregrine Falcons used at least three broad, general routes south from the breeding areas, and individuals stopped migrating as far north as the U.S.A. mid-Atlantic coast and as far south as central Argentina. The radiomarked Peregrine Falcons used coastal routes, mid-continental routes, and water-crossing routes: the Davis Strait and Caribbean Sea. During northward migration, Peregrines migrating through at Padre Island, Texas diverged for destinations from central Alaska across the continent to central West Greenland. Swainson's Hawks migrated an average of about 13,504 km southward and 11,952 km northward, and travelled 188 km/d southward and 150 km/d northward. Swainson's Hawks converged in eastern Mexico on the Gulf of Mexico coast. Southward, these hawks followed a narrow, well-defined path through Central America, across the Andes Mountains in Columbia, and east of the Andes to central Argentina where they all spent the austral summer. Swainson's Hawks northward migration largely retraced their southward route.

Journal of Avian Biology↗
USGS1982

The peregrine falcon in Arizona: Habitat utilization and management recommendations

The peregrine falcon once bred in significant numbers in Arizona. Good documentation is available for specific breeding sites and an additional 20 general locations. This report, based on the published literature, an extensive personal contact survey, an aerial habitat inventory (over 124 hours air time), and ground visits to over 300 locations, provides information on habitat preferences and management practices which can contribute to the bird's survival. In seeking to identify the habitat preferences of the falcon, many site description factors were examined. Those traits which appeared common to most recent Arizona sites (and therefore most useful in evaluating habitat) were: elevation less than 9,000 feet, cliffs tall or very tall, cliffs extensive, topographic relief high, and surface water readily available. All recent sites are in extensive canyon systems or in extensive mountain ranges. Using a habitat evaluation key derived from the traits common to known breeding sites, all cliff regions in Arizona and the Navajo Indian Reservation were flown and evaluated for suitability. Nineteen falcon eyries located in subsequent ground visits were all in areas previously ranked acceptable or better. Many management alternatives are discussed: management of information on breeding sites, habitat preservation, controlling disruptive human activities, and enhancing productivity through the creation of suitable breeding ledges, providing pesticide free prey, or direct reintroductions. Given their privacy (and an increasingly pesticide free environment) the peregrine falcon will likely exist indefinitely in suitable areas across Arizona.

Institute for Raptor Studies Research Reports↗
USGS1995

The Altay falcon: Origin, morphology and distribution

The systematic position of the Altay falcon (Falco altaicus lorenzi) is perhaps the most enigmatic question lingering in falcon taxonomy. First reported to science in 1811, it has been treated as a race of the gyrfalcon (F. rusticolus), as a race of the saker (F. cherrug), as two separate species (F. lorenzi and F. altaicus), and as one to three color morphs of either the saker or the gyrfalcon. Ironically, two or even more of these explanations may be correct. Of 53 specimens examined, at least two are misidentified gyrfalcons, a score I dismiss as typical sakers, but a sizeable group (N = 34) is retained as representing what I consider to be the true Altay falcon type. Three adult color morphs exist: red, brown and grey. The red-backed morph closely resembles some eastern sakers. The chocolate morph resembles the black gyrfalcon from Labrador. The grey morph resembles the grey morph of the gyrfalcon. Ecological, geographical and morphological information contribute to the conclusion that this core group represents a gyrfalcon-saker hybrid that is very likely being swamped into obscurity through back crosses with the saker. The breeding range reported herein (Altay-Sayan Mountains) is greatly contracted from that previously reported. The true identify of the Altay falcon will be resolved by molecular genetics.

Book chapter↗
USGS2017

Are nest boxes ecological traps for red-footed falcons Falco vespertinius at Naurzum

Nest box programs are frequently implemented for conservation of cavity-nesting birds, but their effectiveness is rarely evaluated in comparison to birds not using nest boxes. In the European Palearctic, Red-Footed Falcon ( Falco vespertinus ) populations are both of high conservation concern and are strongly associated with nest box programs in heavily managed landscapes. We used a 21-year monitoring dataset developed from monitoring 753 nesting attempts by Red-footed Falcons at the Naurzum Zapovednick to evaluate response of demographic parameters of Redfooted Falcons to environmental factors including use of nest boxes. Variations in lay date and in numbers of eggs were not well explained by any one model, but instead by combinations of models with terms for nest type, land cover type and degree of coloniality. In contrast, variation in both offspring loss and numbers of fledglings produced were fairly well explained by a single model including terms for nest type, land cover type, and an interaction between the two parameters (65% and 81% model weights respectively). Because, for other species, early lay dates are associated with individual fitness, this interaction highlighted a potential ecological trap where falcons using nest boxes on forest edges at Naurzum lay eggs earlier but suffer greater offspring loss and produce lower numbers of fledglings than do those in other nesting settings.

Kostanay Oblast↗
USGS2000

Species variation in osmotic, cryoprotectant, and cooling rate tolerance in poultry, eagle, and Peregrine Falcon spermatozoa

Potential factors influencing spermatozoa survival to cryopreservation and thawing were analyzed across a range of the following avian species: domestic chicken ( Gallus domesticus ), domestic turkey ( Meleagris gallopavo ), golden eagle ( Aquila chrysaetos ), Bonelli’s eagle ( Hieraaetus fasciatus ), imperial eagle ( Aquila adalberti ), and peregrine falcon ( Falco peregrinus ). Studies focused on spermatozoa tolerance to the following: 1) osmotic stress, 2) different extracellular concentrations of the cryoprotectant dimethylacetamide (DMA), 3) equilibration times of 1 versus 4 h, 4) equilibration temperature of 4 versus 21°C, and 5) rapid versus slow cooling before cryopreservation and standard thawing. Sperm viability was assessed with the live/dead stain (SYBR-14/propidium iodine). Sperm viability at osmolalities ≥800 mOsm was higher ( P < 0.05) in raptor than poultry semen. Return to isotonicity after exposure to hypertonicity (3000 mOsm) decreased ( P < 0.05) number of viable spermatozoa in chicken, turkey, and golden and Bonelli’s eagle spermatozoa but not in imperial eagle or peregrine falcon spermatozoa. Differences were found in spermatozoa resistance to hypotonic conditions, with eagle species demonstrating the most tolerance. Semen, equilibrated for 1 h (4°C) in diluent containing DMA (≥2.06 M), experienced decreased ( P < 0.05) spermatozoa survival in all species, except the golden eagle and peregrine falcon. Number of surviving spermatozoa diminished progressively with increasing DMA concentrations in all species. Increased equilibration temperature (from 4 to 21°C) markedly reduced ( P < 0.05) spermatozoa survival in all species except the Bonelli’s eagle and turkey. Rapid cooling was detrimental ( P < 0.05) to spermatozoa from all species except the imperial eagle and the chicken. These results demonstrate that avian spermatozoa differ remarkably in response to osmotic changes, DMA concentrations, equilibration time, temperature, and survival after fast or slow freezing. These differences emphasize the need for species-specific studies in the development and enhancement of assisted breeding for poultry and endangered species.

Biology of Reproduction↗
USGS1999

Siblicide, splayed-toes-flight display, and grappling in the Saker Falcon

We observed two incidents of novel social behavior in the saker falcon (Falco cherrug) in Mongolia. First, we provide an account of a two-week-old saker falcon chick killing its nest mate, the first direct observation of siblicide in the genus Falco. We also report aerial combat between three adult saker falcons including observations of talon grappling, whirling, and Splayed-toes-flight, a previously undescribed social display.

Journal of Raptor Research↗
USGS2021

Red-footed Falcon Falco vespertinus

Red-footed falcons (Falco vespertinus) are a small, long-distance and obligate migrant falcon that breeds at the forest-steppe interface in Eurasia and winters in Southern Africa. Research carried out with geolocators and satellite transmitters show that during the southbound migration Central Asian birds migrate through the Caucasus and the Middle East, while those from Eastern Europe cross the Eastern Mediterranean. Once in Africa, they cross the Sahara, the Sahel, where they perform short stopovers, and the Congo rainforest or the Rift valley, heading towards the wintering grounds. Northbound migration involves stopovers in West Africa and long crossings over the Mediterranean Sea. Both visual observations and tracking studies show that at least some populations of the species perform a clockwise loop migration that involves extensive longitudinal movements and. for some sub-populations, crossing the Central Mediterranean only during spring. Pre-breeding migration has a longer duration than post-breeding migration, probably because stopovers are longer and wind assistance lower. Red-footed falcons also face substantial anthropogenic threats along migration, particularly the risk of shooting at migratory bottlenecks.

Book chapter↗
USGS2020

Isolation and characterization of microsatellite loci in merlins (Falco columbarius) and cross-species amplification in gyrfalcons (F. rusticolus) and peregrine falcons (F. peregrinus)

I. Background: Merlins, Falco columbarius, breed throughout temperate and high latitude habitats in Asia, Europe, and North America. Like peregrine falcons, F. peregrinus, merlins underwent population declines during the mid-to-late 20th century, due to organochlorine-based contamination, and have subsequently recovered, at least in North American populations. II. Methods and Results: To better understand levels of genetic diversity and population structuring in contemporary populations and to assess the impact of the 20th century decline, we used genomic data archived in public databases and constructed genomic libraries to isolate and characterize a suite of 17 microsatellite markers for use in merlins. We also conducted cross-amplification experiments to determine the markers’ utility in peregrine falcons and gyrfalcons, F. rusticolus. III. Conclusions: These markers provide a valuable addition to marker suites that can be used to determine individual identity and conduct genetic analyses on merlins and congeners.

Molecular Biology Reports↗
USGS2026

Status assessment of peregrine falcons in North America using integrated population models

Species status assessments require an understanding of underlying population dynamics and important drivers of species demography. Large-scale assessments can be difficult due to challenges collating data obtained through different methods and different sources at multiple scales. Integrated population models (IPMs) provide a unified framework to combine multiple data sources and jointly estimate population parameters over a large spatiotemporal scale. We developed separate IPMs to estimate abundance and demographic rates for a northern (NMP) and southern (SMP) management population of peregrine falcons ( Falco peregrinus ) in North America from 2008 through 2019 (SMP) and 2020 (NMP). An outbreak of highly pathogenic avian influenza (HPAI) starting in 2021 led us to extend our modeling effort to assess its impact on these management populations by updating both IPMs using index data of population size through 2024 in a predictive framework. Survival probabilities differed drastically between first-year and after-first-year individuals in both management populations. After-first-year survival was nearly identical between the NMP and SMP, but first-year survival was lower in the SMP. Mean productivity was significantly lower in the NMP compared to the SMP, whereas the probability of breeding was similar in both management populations. Estimated total abundance for the NMP was substantially larger than the SMP, representing most of the North American peregrine population. Population growth was positive for both management populations, albeit at a slower rate for the NMP. The NMP declined from 2017 to 2018 coinciding with a drop in 2018 estimated productivity. When we extended the IPMs with updated count data through 2024, the NMP slightly declined but estimated abundance remained above levels at the start of the time series analyzed. The SMP grew at a similar rate to that predicted during the period informed by demographic data. We did not detect a continental-scale change in population size or trajectory in either management population associated with the arrival of HPAI in 2021. Further monitoring can support determination of whether the declines in the NMP were temporary, can enhance understanding of the underlying mechanisms, and can be used to guide the conservation and management of the peregrine falcon population in North America.

North America↗
USGS2019

Elevated heterozygosity in adults relative to juveniles provides evidence of viability selection on eagles and falcons

Viability selection yields adult populations that are more genetically variable than those of juveniles, producing a positive correlation between heterozygosity and survival. Viability selection could be the result of decreased heterozygosity across many loci in inbred individuals and a subsequent decrease in survivorship resulting from the expression of the deleterious alleles. Alternatively, locus-specific differences in genetic variability between adults and juveniles may be driven by forms of balancing selection, including heterozygote advantage, frequency-dependent selection, or selection across temporal and spatial scales. We use a pooled-sequencing approach to compare genome-wide and locus-specific genetic variability between 74 golden eagle ( Aquila chrysaetos ), 62 imperial eagle ( Aquila heliaca ), and 69 prairie falcon ( Falco mexicanus ) juveniles and adults. Although genome-wide genetic variability is comparable between juvenile and adult golden eagles and prairie falcons, imperial eagle adults are significantly more heterozygous than juveniles. This evidence of viability selection may stem from a relatively smaller imperial eagle effective population size and potentially greater genetic load. We additionally identify ~2000 single-nucleotide polymorphisms across the 3 species with extreme differences in heterozygosity between juveniles and adults. Many of these markers are associated with genes implicated in immune function or olfaction. These loci represent potential targets for studies of how heterozygote advantage, frequency-dependent selection, and selection over spatial and temporal scales influence survivorship in avian species. Overall, our genome-wide data extend previous studies that used allozyme or microsatellite markers and indicate that viability selection may be a more common evolutionary phenomenon than often appreciated.

Journal of Heredity↗
USGS2015

Multi‐season occupancy models identify biotic and abiotic factors influencing a recovering Arctic Peregrine Falcon Falco peregrinus tundrius population

Critical information for evaluating the effectiveness of management strategies for species of concern include distinguishing seldom occupied (or low‐quality) habitat from habitat that is frequently occupied and thus contributes substantially to population trends. Using multi‐season models that account for imperfect detection and a long‐term (1981–2002) dataset on migratory Arctic Peregrine Falcons Falco peregrinus tundrius nesting along the Colville River, Alaska, we quantified the effects of previous year's productivity (i.e. site quality), amount of prey habitat, topography, climate, competition and year on occupancy dynamics across two spatial scales (nest‐sites, cliffs) during recovery of the population. Initial occupancy probability was positively correlated with area of surrounding prey habitat and height of nest‐sites above the Colville River. Colonization probability was positively correlated with nest height and negatively correlated with date of snowmelt. Local extinction probability was negatively correlated with productivity, area of prey habitat and nest height. Colonization and local extinction probabilities were also positively and negatively correlated, respectively, with year. Our results suggest that nest‐sites (or cliffs) along the Colville River do not need equal protection measures. Nest‐sites and cliffs with historically higher productivity were occupied most frequently and had lower probability of local extinction. These sites were on cliffs high above the river drainage, surrounded by adequate prey habitat and with southerly aspects associated with early snowmelt and warmer microclimates in spring. Protecting these sites is likely to encourage continued occupancy by Arctic Peregrine Falcons along the Colville River and other similar areas. Our findings also illustrate the importance of evaluating fitness parameters along with climate and habitat features when analysing occupancy dynamics, particularly with a long‐term dataset spanning a range of annual climate variation.

Alaska↗
USGS2022

The DDT-induced decline influenced genetic diversity in naturally-recovered peregrine falcons (Falco peregrinus) nesting within the Alaska Arctic and eastern Interior

We assessed the influence of the severe mid-20 th century population decline on genetic diversity in non-augmented peregrine falcon ( Falco peregrinus ) populations nesting within Alaska Arctic and eastern Interior. Microsatellite and mitochondrial DNA (mtDNA) data were analyzed for peregrine falcons sampled from three periods: pre-decline, decline, and post-decline. The influence of the decline on genetic diversity differed between the two locales. Alaska Arctic was characterized by shifts in mtDNA haplotype frequencies, increased inbreeding coefficient, reduction in effective population size, and increase in private haplotypes, and a signature of post-decline population growth was detected, while eastern Interior showed a reduction in haplotype diversity, no differences in allelic or haplotypic frequencies between pre- and post-decline periods, though pre-decline birds clustered away from the other two periods and allelic frequency differences were observed between decline and post-decline periods. Patterns in genetic diversity suggest populations recovered through recruitment from within and immigration.

Alaska↗
USGS2011

Lack of genetic polymorphism among peregrine falcons Falco peregrinus of Fiji

We compared levels of genetic diversity and isolation among peregrine falcons Falco peregrinus from two South Pacific island complexes (Fiji and Vanuatu: F. p. nesiotes ), relative to other island and mainland populations. Fragment data from 12 microsatellite loci and sequence information from the control region of the mitochondrial DNA indicated levels of genetic variation in the South Pacific populations were lower than other island and mainland populations. Indeed, diversity varied from extremely low (Vanuatu) to completely absent (Fiji). We find little support for a hypothesis that populations on Fiji or Vanuatu were colonized via Australia. The complete lack of polymorphism in peregrine falcons of Fiji is remarkable, and to our knowledge has not been observed in a natural avian population. This lack of polymorphism, and the inability to test for decrease in polymorphism using museum samples, precludes testing whether the lack of genetic diversity in the population on Fiji is due to a recent bottleneck, or sustained isolation over evolutionary time. Increased fertility in eggs of Fiji peregrines upon outbreeding with males from other areas is consistent with inbreeding depression within a population typified by heterozygote deficiency.

Journal of Avian Biology↗