Male Falcons Research Articles

First Biochemical Comparison Between Saker Falcon Subspecies Falco cherrug cherrug and Falco cherrug milvipes

Abstract We collected blood samples from 44 Western Saker Falcons (Falco cherrug cherrug) and 68 Eastern Saker Falcons (Falco cherrug milvipes) in captivity at two facilities in Bulgaria to evaluate the health of individuals involved in a reintroduction project, and to gain insight into appropriate veterinary care and treatment of the birds. We compared the values of 18 biochemical parameters between the two subspecies and also between females and males. We found significant differences between the two subspecies for some of the parameters tested; however, they likely resulted from different feeding regimes at the two breeding facilities—one housing most of the Western Saker Falcons and the other all the Eastern Saker Falcons. Further tests should compare the biochemical values between birds of the two subspecies housed in the same facility. We also found significant differences in the biochemistry of female and male falcons across some parameters tested. After 20 yr without a record of Saker Falcons (Falco cherrug) nesting in Bulgaria, this globally endangered species has been successfully breeding there since 2018 as a result of an ongoing reintroduction project. By establishing baseline information on the differences in the biochemistry of Saker Falcons, our research may guide future studies of this rare species and aid veterinary care and treatment of the birds breeding in captivity.

Water visitation patterns by Eleonora’s falcon at its breeding grounds: a case study using visual observations and camera traps

Water is a vital resource providing multiple services to many organisms, including birds. Eleonora’s falcon is an iconic, long-distance migrant bird of the Palearctic region. While various aspects of its life history have been thoroughly studied, its dependence on water sources has been poorly documented. In this study, we examine for the first time the species’ visitation patterns at a complex of small, natural ponds of karstic water on a Greek island and provide a detailed description of its bathing and drinking behaviour using visual observations and camera traps. Our results indicate that the species visits the ponds systematically from spring until autumn to bathe and drink. Water visitation patterns suggest communal behaviour, most probably benefitting from increased vigilance in greater numbers. In spring, male falcons prevail during water sessions and the reverse pattern is observed in autumn, whereas morph ratio remains stable, close to the expected 3:1 ratio. Temperature, affecting the falcons’ foraging activity and/or their heat dissipation requirements, together with seasonal differences in labour division between sexes can explain a significant amount of the observed variability in water visitation patterns. Freshwater sources in most islets hosting breeding colonies are scarce, thus natural ponds in nearby larger islands are an important resource many falcons could rely on while at their breeding grounds. The identification and preservation of bathing and drinking spots where falcons gather in numbers across its breeding range is thus highly recommended. Considering the forecasted impact of climate change on karstic water we also encourage an in-depth analysis of the role of water in the adaptation of Eleonora’s falcon to a life in insular environments experiencing global warming. Last but not least, further investigation of the species’ communal behaviour regarding water use can also offer interesting insights in the species’ natural history. HIGHLIGHTS•Eleonora’s falcons visit the water ponds systematically and communally to bathe and drink •Temperature variability and differences in labour division between sexes explain water visitation patterns to a large extent

Long-term demography of a reintroduced population of endangered falcons

We examined long-term demography of an endangered subspecies, the Northern Aplomado Falcon ( Falco femoralis septentrionalis ), in South Texas, USA. The population has been managed and monitored since reintroductions began in 1993. Data spanning 1993–2018 enabled us to build an integrated population model (IPM) and a Cormack-Jolly-Seber model to estimate survival for three life stages (first-year, non-breeders, and breeders) and both sexes, abundance of males, fecundity, immigration, and emigration. Male falcons survived at lower rates than females during their first year; Hurricane Harvey caused a decline in survival rates of first-years and breeders; and fecundity increased after 2011 coinciding with changes in management focused on improving nest platforms and habitat quality. Both immigration of non-breeders and emigration were likely negligible for this population suggesting a potentially isolated population. The IPM likely overestimated immigration of breeders warranting further research. Population growth rates were greatest during years having more released captive-reared young and greater probabilities of breeder survival. Importantly, an apparent decrease in breeder survival of unknown cause occurred during 2006–2009 when breeder survival declined and remained low for several years. Our ability to identify the cause for reduced survival is now greatly hampered by the extended time that has passed, limiting the usefulness of this recent awareness for informing management and further highlighting the importance of real-time monitoring for proactive decision making processes. Our study greatly improves knowledge of demographics for a reintroduced, isolated, and intensively managed population of Aplomado Falcons. Applying this IPM to new data each year will enable adaptive management of the South Texas population by providing annual evaluations of vital rates along with revised assessments of monitoring and management. • We created an IPM to evaluate vital rates and management of Aplomado Falcons. • Hurricane Harvey caused a decline in survival of first-years and breeders. • Emigration was trivial, and immigration was likely trivial but needs more study. • Breeder survival was an important vital rate, and declined during 2006–2009. • Management of artificial nest boxes, habitat, and hacking improved vital rates.

Natal Dispersal of Aplomado Falcons in Chihuahua, Mexico

The persistence of a species throughout its geographic range requires dispersal among its populations. The study of dispersal is particularly relevant for species whose geographic range has contracted, such as the endangered Northern Aplomado Falcon (Falco femoralis septentrionalis). We used Argos 5-g PTT-100 satellite transmitters to determine the movements of two wild Chihuahuan Desert Aplomado Falcons (one female and one male) from fledging to breeding (male), or transmitter failure (female), at 1062 d and 439 d of age, respectively. Both falcons dispersed from their natal territories 2–3 mo after fledging. These falcons then wandered between activity centers near historic breeding territories and some territories recently converted to farmlands. These two falcons also explored areas outside known breeding areas via some long-distance movements to areas of potential breeding habitat being converted to farmland. In 2 yr, movements of the male covered 7412 km2. This falcon nested unsuccessfully with an unbanded female in a vacant breeding territory 15 km from his natal site. His nesting attempt the following year yielded two fledglings. While a breeding bird, the male falcon had a home range of 200 km2. For 17 mo, the female falcon wandered through an area of 12,136 km2. The farthest distance she traveled from her nest site prior to transmitter failure was 154 km.

Sex interacts with age-dependent change in the abundance of lice-infesting Amur Falcons (Falco amurensis)

Sex-biassed and age-biassed parasite infections are common in nature, including ectoparasites-vertebrate host systems. We investigated the effect of Amur Falcons’ sex, age and body size on the abundance of their lice at a migratory stopover site, where the falcons’ habitat use and behaviour are more homogeneous across sex and age categories than during the breeding season. We sampled Amur Falcons in Nagaland, India at major roosting sites in 2016. We applied generalized linear models (with negative binomial distribution and log-link) to model the abundance of their two most numerous lice (Colpocephalum subzerafae and Degeeriella rufa) using the host age category (juvenile or adult) and wing length, both in interaction with sex, as explanatory variables. The abundance of C. subzerafae was only affected by host age, being nearly four times higher on juveniles than on adults. Juveniles were also more infested with D. rufa than the adults. Additionally, the abundance of the latter species was lower on adult male Falcons as compared to adult females. A juvenile bias in ectoparasite infestations is common in nature, probably due to juveniles being immunologically naïve, more resource-limited and may be inexperienced in body maintenance behaviours like preening and grooming. On the other hand, female-biassed infestations are much rarer than male-biassed infestations. We briefly discuss the possible causes of female-biassed infestations on Amur Falcons reported here, and in the closely related Red-footed Falcon and Lesser Kestrel as reported in the literature.

Natal Dispersal of Aplomado Falcons in Chihuahua, Mexico

The persistence of a species throughout its geographic range requires dispersal among its populations. The study of dispersal is particularly relevant for species whose geographic range has contracted, such as the endangered Northern Aplomado Falcon (Falco femoralis septentrionalis). We used Argos 5-g PTT-100 satellite transmitters to determine the movements of two wild Chihuahuan Desert Aplomado Falcons (one female and one male) from fledging to breeding (male), or transmitter failure (female), at 1062 d and 439 d of age, respectively. Both falcons dispersed from their natal territories 2–3 mo after fledging. These falcons then wandered between activity centers near historic breeding territories and some territories recently converted to farmlands. These two falcons also explored areas outside known breeding areas via some long-distance movements to areas of potential breeding habitat being converted to farmland. In 2 yr, movements of the male covered 7412 km2. This falcon nested unsuccessfully with an unbanded female in a vacant breeding territory 15 km from his natal site. His nesting attempt the following year yielded two fledglings. While a breeding bird, the male falcon had a home range of 200 km2. For 17 mo, the female falcon wandered through an area of 12,136 km2. The farthest distance she traveled from her nest site prior to transmitter failure was 154 km.

Falcon Adenovirus Infection in Breeding Taita Falcons (Falco Fasciinucha)

Four female and 3 male Taita falcons (Falco fasciinucha) out of a breeding colony of 14 Taita falcons (7 pairs) died during the breeding season after showing lethargy and anorexia for 1 to 2 days. All animals were submitted for necropsy. Gross lesions in the female falcons were characterized by anemia secondary to marked hemorrhage into the ovary and oviduct, serofibrinous effusion into the cardioabdominal cavity and serosal petechiae. In addition, marked necrotizing splenitis and pulmonary hemorrhage were present. Histologically, the female falcons had mild necrotizing hepatitis with numerous intranuclear inclusion bodies and necrotizing splenitis with rare inclusion bodies. There were no gross lesions in the male falcons, and the histological lesions were characterized by urate deposition and rare intranuclear inclusion bodies in the renal tubular epithelial cells. Adenoviral particles were found by electron microscopy in the cloacal contents of the female Taita falcons but not in the male falcons. DNA in situ hybridization revealed widespread aviadenoviral nucleic acid within the nuclei of hepatocytes, renal tubular epithelial cells, and adrenal cells in the female falcons but no aviadenoviral nucleic acid in 1 male falcon and only a low quantity of adenoviral nucleic acid in the liver and kidney of another male Taita falcon. PCR amplified aviadenoviral DNA in the liver and intestine of all Taita falcons. The amplicons were sequenced, and the virus was identified as falcon adenovirus. The deaths of the female and male birds were attributed to the aviadenovirus infection.

Soaring Flight in the Eleonora's Falcon (Falco eleonorae)

AbstractEleonora's Falcon (Falco eleonorae) breeds in the Mediterranean region and is highly adapted for catching small birds on passage migration between Eurasia and their African winter quarters, which they feed their young. We studied gliding flight behavior of Eleonora's Falcon at a breeding colony located on a small island southwest of Sardinia, Italy. Gliding and soaring flight performance was measured using an optical range finder and evaluated against flight mechanical theory. The male falcon does the majority of hunting and usually sets off from the colony to hunting areas located at high altitude over the open sea to catch prey. To lower the cost of transport and maximize the energy gain from hunting, we show that the birds use vertical winds for soaring when available. The occurrence of rising air changes with wind direction. At north-northwesterly winds (on-shore), slope lift is available outside the nesting cliffs, and at south-southeasterly winds thermals that form over the island drift out over the sea. Our observations demonstrated the flexibility of flight behavior in relation to the wind situation, and birds thereby make full use of available soaring conditions.

Soaring Flight in the Eleonora's Falcon (Falco eleonorae)

Abstract Eleonora's Falcon (Falco eleonorae) breeds in the Mediterranean region and is highly adapted for catching small birds on passage migration between Eurasia and their African winter quarters, which they feed their young. We studied gliding flight behavior of Eleonora's Falcon at a breeding colony located on a small island southwest of Sardinia, Italy. Gliding and soaring flight performance was measured using an optical range finder and evaluated against flight mechanical theory. The male falcon does the majority of hunting and usually sets off from the colony to hunting areas located at high altitude over the open sea to catch prey. To lower the cost of transport and maximize the energy gain from hunting, we show that the birds use vertical winds for soaring when available. The occurrence of rising air changes with wind direction. At north-northwesterly winds (on-shore), slope lift is available outside the nesting cliffs, and at south-southeasterly winds thermals that form over the island drift out...

Hunting Flight Behaviour of the Eleonora's Falcon Falco eleonorae

The Eleonora's Falcon Falco eleonorae breeds on islands and islets in the Mediterranean region and feeds its young on migratory birds caught in the air. The breeding season is scheduled to coincide with the peak of bird migration. Between 12 and 20 September 1997 we measured flight tracks of falcons within a range of 4 km from their breeding cliffs on Isola di San Pietro 6 km off the south-west coast of Sardinia, by using an optical range finder. The male falcons left the colony in directions between W and NW to hunt far off-shore, probably intersecting migrants departing from mainland Europe in southern France. Flight tracks of falcons leaving for off-shore hunting and falcons searching for prey closer to the colony differed significantly, as revealed by a straightness index. Falcons leaving the colony for the far off-shore hunting area climbed to altitudes over 1000 m. The highest altitude recorded was 1649 m. The altitudes reported from radar studies on nocturnal migrants in the Mediterranean match the flight altitudes observed in the departing Eleonora's Falcons. Calculations based on the times taken for falcons to return with prey to the nest indicate a maximum distance to the hunting area of about 24 km. The falcons compensated partially for wind drift caused by cross winds when departing for off-shore hunting. Complete compensation might not be possible if the wave pattern of the sea is used for orientation, due to movements of the reference system relative the ground. The flight time of Eleonora's Falcons did not seem to be severely restricted by a metabolic ceiling, although such a ceiling does not allow extensive day and night hunting.

A Comment on Incubating Male Falcons

A Comment on Incubating Male Falcons