Peregrine Falcon Population Research Articles

Avian wings can lengthen rather than shorten in response to increased migratory predation danger.

Increasing predation danger can select for safety-enhancing modifications to prey morphology. Here, we document the multi-decade wing lengthening of a Pacific flyway migrant, the western sandpiper (Calidris mauri), and contrast this with contemporaneous wing shortening of the closely related semipalmated sandpiper (C. pusilla) on the Atlantic flyway. We measured >12,000 southbound western sandpipers captured from 1978 to 2020 at a major stopover site in British Columbia. Wing length increased at 0.074 mm year-1 (SE = 0.017; p < .0003) for adults, and 0.087 mm year-1 (SE = 0.029; p < .007) for juveniles. These rates are of similarly large magnitude (4%-5% overall), but opposite in direction, to the rate we previously reported for semipalmated sandpiper adults (-0.103 mm year-1). In both species, the change is specific to wings rather than being part of a general body size change. We interpret both trends as responses to the ongoing strong increase of peregrine falcon (Falco peregrinus) populations since the mid-1970s, an important predator encountered by these species in contrasting ways during migration. Western sandpipers and peregrine migrations have temporal and spatial overlap. Longer wings enhance migratory speed and efficiency, enabling western sandpipers to decrease overlap by advancing to safer zones ahead of falcon passage. In contrast, semipalmated sandpipers primarily encounter peregrines as residents at migratory staging sites. Shorter wings improve acceleration and agility, helping migrants to escape attacks. Juvenile western sandpiper wing length also shows a component additive to the lengthening trend, shifting between years at 0.055 mm day-1 with the highly variable snowmelt date, with wings shorter following early springs. On the Pacific flyway, the timing of peregrine southward passage advances with snowmelt, increasing the relative exposure of juveniles to post-migratory resident peregrines. We interpret this annual wing length adjustment as an induced defense, made possible because snowmelt timing is a reliable cue to danger in the upcoming migration.

Temporal variation in the peregrine falcons (Falco peregrinus) diet after the extinction of the original population and the emergence of a new population in Slovakia

Abstract We made an analysis of the osteological remains of prey that had been captured by the peregrine falcon (Falco peregrinus) and was collected from eyries perched high in rocky cliffs of Slovakia. Birds dominated the 7,233 vertebrates identified (class Aves, with minimum of 98 species and 97.2% of the total). Bones from mammals (class Mammalia, 24 species, 2.5%) were rarely found, and sporadic remains from lower vertebrate species (classes Amphibia, Reptilia, Pisces, 0.3%) were also noted. The collected specimens were divided over three distinct periods. Before domestic pigeons became a major component in the juvenile peregrine falcon diet (Period A), wild pigeons and doves were the most common prey; specifically stock doves (Columba oenas) caught at lower elevations, and wood pigeons (Columba palumbus) in mountainous areas. The Eurasian woodcock (Scolopax rusticola) was a frequent prey . The diversity of peregrine falcon diet reached its maximum between the 1930s and the 1950s (Period B), with the domestic pigeon (Columba livia domestica) present in the diet at a similar abundance (16.1%) to wild pigeons and doves. The peregrine falcon population tailed off in the 1960s as pesticides became more commonly used in agriculture. A new population started expanding from Western Europe during the 1990s and has stabilised at around 150 breeding pairs in recent years. Since the turn of the millennium (Period C), domestic pigeons have become the dominant prey (51.1%) along with smaller songbirds such as hawfinches (Coccothraustes coccothraustes) and common starlings (Sturnus vulgaris), at 15.5% and 14.6% of total osteological remains collected, respectively.

Environmental conditions experienced upon first breeding modulate costs of early breeding but not age-specific reproductive output in peregrine falcons.

Although once considered uncommon, there is growing evidence of widespread senescence in wildlife populations. However, few studies have examined the traits involved, inter-sexual differences, and environmental correlates of age-specific performance in raptors. We studied age-specific reproductive performance and actuarial senescence (decrease in survival probability with age) in a peregrine falcon population monitored for 21 years. We analysed changes with age in the number of offspring produced and incubation start date. We also inspected variation in lifespan and breeding lifespan (number of breeding occasions in a lifetime). In every case, we assessed associations between variations in traits and age, sex, recruitment age, and environmental conditions (cumulative rainfall during breeding season) experienced upon the first breeding attempt. We found scarce evidence for reproductive senescence. Only the incubation start date in females, which was delayed after approximately 8 cy (calendar years), suggested reproductive senescence in our study population. Regarding actuarial senescence, our data did not support it as we only found evidence of higher juvenile mortality. Furthermore, expected lifespan in peregrines recruited at 2 cy was associated with conditions experienced upon the first breeding attempt. The lifespan and breeding career of individuals recruited as yearlings and experiencing low rainfall upon first breeding did not significantly differ from those recruited as adults. However, those recruited as yearlings and experiencing poor environmental conditions upon the first breeding attempt showed reduced lifespan and breeding lifespan.

Spatio-temporal variation in post-recovery dynamics in a large Peregrine Falcon (Falco peregrinus) population in the Jura mountains 2000–2020

Spatio-temporal variation in post-recovery dynamics in a large Peregrine Falcon (Falco peregrinus) population in the Jura mountains 2000–2020

Spatio‐temporal variation in post‐recovery dynamics in a large Peregrine Falcon (Falco peregrinus) population in the Jura mountains 2000–2020†

After spectacular population crashes in the 1960 and 1970s, Peregrine Falcon Falco peregrinus populations recovered worldwide, and in the 2000s many study populations were back to normal. However, post‐recovery trends have been documented less well. We combined three long‐term population studies covering the entire Jura mountain range (16 304 km2) to examine spatio‐temporal variation in population dynamics during 2000–2020 in 420 known nesting sites in five regions: Ain, Jura and Doubs in France, and Jura Sud and Jura Nord in Switzerland. Every year about 60% of all sites were surveyed at least once, and this proportion increased over time. We used Bayesian occupancy modelling to investigate site persistence and colonization probabilities and correct status and trend estimates for bias due to non‐random site coverage. Based on the average of two models correcting for preferential sampling, we estimated that population size peaked in 2002 (Jura), 2005 (Doubs), 2007 (Ain, Jura Nord) and in 2007 for the Jura as a whole. Thereafter, the population declined significantly in four regions and in the Jura as a whole, with the strongest decline found in the Jura Nord ( –38%, 95% credible interval –34%/–41%) during 2007–2020. Thus, we found considerable spatial heterogeneity in post‐recovery trends and widespread post‐recovery declines. Reasons for the latter may include Eagle Owl Bubo bubo predation, illegal persecution and human disturbance. Our results illustrate how quickly positive population trends may be reversed, such that continuous long‐term monitoring even for species seemingly ‘out of danger’ remains invaluable. Our study also emphasizes the importance of correcting for both coverage bias in general and preferential sampling in particular when assessing population trends in studies where not every territory can be surveyed in all years.

Assessment of the Genetic Potential of the Peregrine Falcon (Falco peregrinus peregrinus) Population Used in the Reintroduction Program in Poland.

Microsatellite DNA analysis is a powerful tool for assessing population genetics. The main aim of this study was to assess the genetic potential of the peregrine falcon population covered by the restitution program. We characterized individuals from breeders that set their birds for release into the wild and birds that have been reintroduced in previous years. This was done using a well-known microsatellite panel designed for the peregrine falcon containing 10 markers. We calculated the genetic distance between individuals and populations using the UPGMA (unweighted pair group method with arithmetic mean) method and then performed a Principal Coordinates Analysis (PCoA) and constructed phylogenetic trees, to visualize the results. In addition, we used the Bayesian clustering method, assuming 1–15 hypothetical populations, to find the model that best fit the data. Units were segregated into groups regardless of the country of origin, and the number of alleles and observed heterozygosity were different in different breeding groups. The wild and captive populations were grouped independent of the original population.

Breeding habitat selection of urban peregrine falcons (Falco peregrinus) in London

Abstract Understanding habitat selection by individual animals within their home range is crucial to facilitating their conservation. Peregrine falcon (Falco peregrinus) populations are increasingly urbanised, but little is known about their urban habitat use. In this study, we analysed the breeding habitat selection of peregrine falcons in London, United Kingdom, based on nest site locations identified through records of public sightings submitted to an online database between 2003 and 2018. We found peregrines displayed a preference for nesting in proximity to waterbodies, built-up areas and public parks and gardens, while wooded, agricultural and allotments areas were least preferred. We hypothesise that peregrines seek contrasting topography that proves advantageous for hunting in the vicinity of their nests, resulting in their selection of breeding sites within tall buildings that are adjacent to suitable foraging areas. From these findings, we conclude that (i) social drivers such as demand for green spaces and waterbodies near buildings shape peregrine nesting opportunities in the city and (ii) for urban planning to support conservation, we need further understanding of how each type of greenspace may be used differentially by raptors.

Home Range of an Adult Female Peregrine Falcon (Falco peregrinus) during the Breeding and Non-breeding Seasons in Kentucky, USA

The peregrine falcon (Falco peregrinus) is a Species of Greatest Conservation Need in Kentucky's State Wildlife Action Plan. The Kentucky Department of Fish and Wildlife Resources has monitored Kentucky's peregrine falcon population since 1997. However, research on the movements, habitat use, and breeding and non-breeding home range of Kentucky's nesting peregrine falcons is lacking. In this study, we used a solar-powered platform transmitter terminal (PTT) with global positioning system (GPS) and Argos capabilities to monitor the movements of a single adult, breeding female, peregrine falcon from 7 June 2015 to 4 May 2018. We found that the female falcon spent the majority of her time in close proximity to the nest site throughout the breeding and non-breeding season. Seasonal home range varied significantly with the largest home range size estimated during the post-fledging period, followed by the non-breeding season, and the smallest home range occurring during the pre-fledge period of the breeding season. We suspect that the increase in home range size observed during the post-fledging period can be attributed to parental care and post-fledge dependency of young.

Influence of the Eagle Owl (Bubo bubo) on the Peregrine Falcon (Falco peregrinus) population in Germany

Abstract In Germany, the Eagle Owl is the only animal species that has a massive impact on the distribution and breeding success of the Peregrine Falcon. Both species compete for the same breeding sites on rocks. In addition, the Peregrine Falcon belongs to the prey spectrum of the Eagle Owl. The Eagle Owl always dominates at places where the two species meet. Since the 1980s, the Eagle Owl has taken over many of the rock face breeding sites of the Peregrine Falcon in Germany. This trend towards the taking-over of Peregrine Falcon nesting sites is ongoing in areas with rocks, as not all regions of Germany have yet been completely colonized by Eagle Owls. Since 1975, the Eagle Owl initially nested on buildings in rural areas, but it is now also colonizing urban areas. Eagle Owls are more and more frequently taking over Peregrine Falcon nest boxes on buildings. The currently growing Peregrine Falcon breeding population on buildings is expected to decline in coming years due to predation by the Eagle Owl, even though these owls do not breed very successfully on buildings and many old and young owls are killed. These statements apply to large parts of Germany. In other areas of Europe, the future usage of buildings as Eagle Owl breeding sites can be expected to have an impact on the Peregrine Falcon populations there. At least eight other Peregrine Falcon breeding sites on buildings and rocks have been taken over by Egyptian Geese (Alopochen aegyptiaca).

Monitoring of Peregrine Falcons in the Ariège Pyrenees and Toulouse, Midi-Pyrénées region, France

Abstract Since the 1980s, the volunteers of the ornithological group of the Nature Midi-Pyrénées association have been monitoring the Peregrine Falcon (Falco peregrinus) population in the Ariège Pyrenees and in the Toulouse agglomeration. The data collected over the last 30 years show stability of the Ariège population: little variation has been observed in brood size, occupation rate of the sites or reproductive success. Only the increasing number of known nesting sites is significant, due to better knowledge of the territory by observers over time. In 2017, the breeding population was estimated to be 24 pairs. Urban monitoring proved the presence of individuals in passage, wintering or resident in Toulouse. Since 2002, downtown Toulouse has been visited by several individuals of both sexes and interactions between males and females have been observed since 2005. Despite the multiplicity of possible eyries or nesting sites in Toulouse, and the massive presence of Peregrine Falcons and dedicated bird watchers, no case of breeding has been reported. In addition to monitoring, measures to protect and support the presence of the species have been put in place. In the Pyrenees, in the light of the growth of human activities near nesting sites, some sites are now subject to official protective measures, coupled with constant vigilance and awareness. In Toulouse, to encourage the breeding of the individuals present, two nesting boxes were installed in 2016, on two buildings frequented by a female and a male. In 2017, a first attempt to reproduce in one of these installations confirmed the value of such developments in urban areas.

Population trends of Peregrine Falcon in Northern Spain – Results of a long-term monitoring project

Abstract We monitored Peregrine Falcon (Falco peregrinus) population in Bizkaia, Northern Spain, during two decades (1998–2017). Our population increased from 34 to 47 territorial pairs, as did other European populations until the first years of the 21st century, and then declined until 34 territorial pairs in 2017. The combination of catastrophic events (Prestige oil spill), increasing rain in winter and spring, and direct and indirect mortality factors significantly affected incubation onset, productivity and population stability, which in turn could impact on the floater population. Rain in February significantly affected incubation onset, which showed a slight positive trend during the last decade. Juvenile females laid 12 days later than adults, and each adult female started incubation in the same dates every year. However, the proportion of juvenile females did not significantly increase as might have been expected. Moreover, productivity was inversely related to incubation onset dates. Rain in April and May also affected productivity, and combined with short term extreme weather events determined a decreasing productivity during the last decade. Moreover, apart from human persecution (which caused 40.30% of the known deaths of Peregrines), we found 18 cases of breeders affected by infectious diseases, also related to weather. The combined effects of these factors, and the low availability of adequate nesting sites, negatively affected (i) territorial populations, (ii) productivity, and (iii) floater population, which in turn also determined territorial population and productivity.

Raptors are still affected by environmental pollutants: Greenlandic Peregrines will not have normal eggshell thickness until 2034

Abstract The DDT-induced effects, eggshell thinning and breeding failure in Peregrine Falcon (Falco peregrinus) populations were reverted with restrictions on the use of the compound from the 1970s, and in most studied populations, the eggshell thickness is back to normal. In Greenland, a previous study of eggshell thinning in Peregrines found that shells had not yet reached pre-DDT levels. In this study, we extend the time series and reinterpret shell thinning data for 196 clutches covering a 45-year time span (1972–2017). There was a significant (P&lt;0.001) increase in the eggshell thickness of 0.23% per year. This corresponds to a change in eggshell thinning from 14.5% to 5.4% in 2017 compared to the pre-DDT mean. With the current rate of change, pre-DDT shell thickness is predicted to be reached around the year 2034. However, a few clutches are still below the critical limit. The relatively slower recovery of the shell thickness in the Greenland population is likely indicative of the slower phasing out of DDT in the Greenlandic Peregrines’ wintering grounds in Latin America. The shell thinning in the Greenlandic population probably never crossed the 17% threshold associated with population declines, contrary to the populations in many other parts of the world.

Results of eighteen years (2000–2017) monitoring study of an extra-alpine Peregrine Falcon Falco peregrinus population in North-Western Italy

Abstract The Author reports the results of a survey about a breeding extra-alpine Peregrine Falcon population in Cuneo Province, NW Italy. The first reproduction was recorded in 2000, and from that year, the monitoring work localized 16 occupied territories in an area of 1,900 km2 covering the hills and nearby lowland areas. The average distance between breeding territories was of 7.6 km with a density 0.7 pairs/100 km2. During the eighteen years, 89 successful breeding attempts were recorded, 81 of them led to fledging of 206 young. Average breeding success was 2.5 juv/reproducing pairs. The nests are located on bridges (motorway viaducts and rail way bridges) and clay/sandstone cliffs. Preliminary prey analyses showed that pigeons and doves represent the 75% of their diet.

Genetic variability in Peregrine Falcon populations of the Western Palaearctic region

Abstract We analysed variation in ten polymorphic microsatellite loci and a portion of cytochrome b gene of mitochondrial DNA in 65 samples from four populations of Peregrine Falcon (Falco peregrinus peregrinus and F. p. brookei) breeding in Northern and Southern Italy, Northern Spain and the Czech Republic to assess genetic diversity in the poorly investigated Western Palearctic region. We added to our cytochrome b sequences a dataset of previously published mtDNA sequences of other populations and subspecies to outline genetic variation in the region on a worldwide basis. Regarding mtDNA we identified 12 haplotypes from our 65 Peregrine Falcon samples, nine of which were new and three already known. The 52% of our samples, including all Italian and Czech specimens, belonged to the previously identified HI haplotype, another 22% of the samples, most of which were from Sicily, showed the new H1 haplotype, while the remaining 26% of the sample partitioned among the other 10 haplotypes. Allelic patterns and genetic structuring of microsatellites were similar to those of other European populations. Genetic differentiation in both mtDNA and microsatellites loci is almost absent and it is not possible to distinguish geographical groups according to taxonomic designation at the subspecies level.

The Danish Peregrine Falcon population: Reestablishment and eggshell thinning

Abstract Denmark being a country with only a few suitable steep nesting cliffs has only harboured a small population of Peregrine Falcons (Falco peregrinus) in historic time. In the previous century, the population gradually declined due to persecution, egg and young collection, and pollution. The last breeding attempt in the 20th century occurred in 1972 in southeastern Denmark. No new breeding attempts were recorded in Denmark until 2001 but since then the population has gradually increased – most rapidly since 2012 – to a peak of 24 territorial pairs in 2018; some of them breeding on man-made structures (nest boxes at bridges and power plants). Here we update the information on the reestablishment of the Peregrine Falcon in Den-mark, including origin and dispersal, reproduction, and eggshell thinning.

Perfluoroalkyl substances (PFASs) and polychlorinated naphthalenes (PCNs) add to the chemical cocktail in peregrine falcon eggs

A suite of perfluoroalkyl substances (PFASs) and polychlorinated naphthalenes (PCNs) were determined in 41 peregrine falcon eggs collected in South Greenland between 1986 and 2014. Median concentrations of perfluorinated sulfonic acids (ΣPFSA) and perfluorinated carboxylic acids (ΣPFCA) were 303 ng/g dry weight (dw) (58 ng/g wet weight, ww) and 100 ng/g dw (19 ng/g ww), respectively, which was comparable to other studies. Perfluorooctane sulfonate (PFOS) accounted for 94% on average of all PFSAs, but did not show a significant time trend. Perfluorohexane sulfonate (PFHxS), perfluoroheptane sulfonate (PFHpS) and perfluorodecane sulfonate (PFDS) showed non-linear decreases over the study period, while some long-chain PFCAs increased significantly. The PCN profile was dominated by the penta-, hexa- and tetrachlorinated congeners CN-52/60, CN-66/67 and CN-42. CN-54, an indicator of combustion, accounted for 2.4% of ΣPCN on average. All PCN congeners showed a decreasing tendency, which was significant for lipid-normalized concentrations of CN-53, CN-54 and CN-63. The ΣPCN median concentration was 21 ng/g lipid weight, which is in the high end of concentrations reported for bird eggs. The PCN and PFAS concentrations add to an already high contaminant burden and a complex chemical cocktail in the peregrine falcon population in Greenland, mainly reflecting contaminant exposure during migration and winter stays in Central and South America.

Recovery and Range Expansion in a North Central Utah Peregrine Falcon Population

Abstract. Peregrine Falcon numbers in much of the Intermountain West rebounded after a decline during the 1950s, 1960s, and early 1970s. However, recent literature regarding the species suggested that little, if any, growth was occurring in populous north central Utah, which once supported a robust Peregrine Falcon population. A concerted reintroduction effort during the 1980s resulted in establishment of nesting pairs of Peregrine Falcons on artificial towers where they were originally released as nestlings, but traditional nesting cliffs generally remained vacant. More recently, numerous Peregrine Falcon pairs have been observed nesting on cliffs both within and adjacent to their historical range in the region. I combined results from recent literature with numbers gleaned during this study to find that 45 Peregrine Falcon nesting territories are documented for the recovery era in north central Utah.

Long-term Reproduction (1984–2013), Nestling Diet, and Eggshell Thickness of Peregrine Falcons (Falco peregrinus) in Yellowstone National Park

Abstract Peregrine Falcons (Falco peregrinus) were extirpated from Yellowstone National Park (YNP) by 1970 as a result of widespread use of DDT (dichloro-diphenyl-trichloroethane) throughout North America from the late 1940s to the early 1970s. DDT, and its primary metabolite DDE (dichloro-diphenyl-dichloroethylene), caused eggshell thinning and impaired reproduction in Peregrine Falcons and other raptors. Restoration of Yellowstone’s Peregrine Falcon population began with nationwide restrictions placed on the use of DDT in 1972, coupled with the release of 36 captive-raised juveniles in YNP and the dispersal of 644 captive-raised juvenile Peregrine Falcons released within 260 km of YNP. We monitored Peregrine Falcon reestablishment and reproductive success in YNP (nesting success, productivity, and brood size) from 1984–2013. Productivity was defined as the number of young reaching ≥28 d per territorial pair. Brood size referred to the number of young reaching ≥28 d per successful pair. From 2010–2013, w...

Origin, Growth, and Composition of the Recovering Peregrine Falcon Population in Ontario

After an absence of more than two decades, Peregrine Falcons (Falco peregrinus) resumed nesting in Ontario in 1986. Between 1991 and 2006, at least 193 young fledged in southern Ontario and 548 young fledged in northern Ontario. The number of breeding pairs, nesting attempts, successful nests, and young fledged all steadily increased in both regions throughout this period. In southern Ontario, 25% of the breeding adults produced nearly 50% of all fledglings, and 87% of the fledglings came from just eight breeding sites. Direction of natal dispersal was variable, but females consistently moved farther than males, and there was frequent movement both to and from adjacent American states. The population recovery resulted from the release of 592 captive-bred F. p. anatum juveniles in Ontario between 1977 and 2005, plus immigration from other provinces and release efforts in adjacent regions of the United States, where at least five subspecies contributed to the gene pool of captive-bred birds. Encounter rates for both captive-bred and wild-fledged young in Ontario have been low, but wild-raised young have been recruited to the breeding population almost twice as frequently as captive-bred birds. This difference partially explains the genetic composition of the southern Ontario population, where at most 21% of nesting attempts between 1995 and 2006 involved a pair of Canadian-released anatum adults, and 59% of cases involved at least one adult of American origin. Therefore, although the Ontario population has exceeded documented historical levels, it may not be greater than actual historical numbers, and it cannot be strictly considered an anatum population.

Productivity, mortality, and management of urban peregrine falcons in northeastern North America

The peregrine falcon (Falco peregrinus) population in eastern North America has grown significantly since the early 1980s, especially in urban areas, but few studies have assessed the factors that influence productivity. We reviewed all documented nesting attempts from southern Ontario, Quebec, Massachusetts, New Jersey, and Pennsylvania from 1980 through 2006 to evaluate these factors. Of 801 nesting attempts, 663 were successful, producing a total of 1,613 young. Mean productivity ranged from 1.7 young fledged per nesting attempt in New Jersey to 2.9 in Quebec. Peregrines nesting in quarries or on buildings had higher productivity than those using marsh towers or bridges, but productivity did not differ overall between urban and rural sites. Nests with overhead cover had higher productivity than those without, as did nests in trays or boxes compared to sites without any human-provided nesting aids. Peregrines favored nest sites facing east to south, but productivity did not vary significantly with direction. Several adults have contributed disproportionately to the growth of the eastern population, with just 5 females and males accounting for 8% and 9% of all young fledged, respectively. Of 160 documented mortalities, we identified cause of death for 118, with the most common being collisions with buildings (36%), vehicles (9%), aircraft (8%), and power lines (8%). In many urban areas, grounded fledglings are rescued and returned to higher perches. Of 85 individuals from southern Ontario that were rescued, at least 8 have subsequently bred, producing 65 known offspring. Although peregrines have been thriving in eastern cities, continued management effort may be required for them to maintain their level of success, with key measures including provision of appropriately located nest boxes and rescue of grounded fledglings. © 2014 The Wildlife Society.