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BIOLOGICAL TRAITS OF THE (FALCO RUSTICOLUS) IN RELATION TO CHANGE

TOM J. CADE

The Peregrine Fund, 5668 West Flying Lane, Boise, ID 83709, USA E-mail: [email protected]

ABSTRACT.—Largest of the true (Falco spp.), the Gyrfalcon (Falco rusticolus) is the north- ernmost diurnal raptor with a circumpolar breeding distribution restricted to and zones between 55º and 82º N. Some migrate south into north temperate zones in win- ter, but others remain in northern latitudes wherever suitable prey occurs. A review of the Gyrfal- con’s ecological relationships and what is known about its population history reveals some vulnerability to the potential effects of climate change on arctic environments, but also some pos- sible mitigating adjustments. The Gyrfalcon relies on two ptarmigan ( spp.) for 50-90% of its diet biomass, so it is likely that an effect of climate change on Gyrfalcons will be mediated through impacts on ptarmigan. The Gyrfalcon has trophic relations with other and that may allow for adjustment to reduced availability of ptarmigan. The Gyrfalcon’s main prey has fluctuated drastically in numbers from year to year; in peak food years a maximum number of pairs nest, but in years with low prey abundance, few breed. Under climate change the 10-year population cycles of ptarmigan and and the 3-4 year cycles of microtine rodents exhibit lower peaks and less regularity. Whether these population changes will persist and what they portend for predators needs study. Historically the Gyrfalcon has been the earliest nesting raptor in the Arctic. Climate change is lengthening the arctic summer, but it is unclear how Gyr- breeding phenology will be influenced by this change. It could be advantageous in spring and autumn by allowing new trophic relationships. Interspecific relations with other raptors nest- ing in the Arctic may be influenced by climate change. The Gyrfalcon and (Falco peregrinus) are potential competitors for nesting sites and food. In West , where nesting peregrines have increased dramatically in the past 50 years and Gyrfalcons have decreased, it has been suggested that the increasing number of peregrines may be forcing gyrs to abandon territories by interference competition over nest-sites or by feeding so persistently on ptarmigan during the breeding season that numbers surviving through winter are insufficient to induce gyrs to lay. The Gyrfalcon and (Falco cherrug) are allopatric populations of closely related groups of falcons. If climate change were to alter biomes so that breeding Gyrfalcons and Saker Falcons come together, interbreeding and extensive introgression of genes likely would occur. Such hybridization might help Gyrfalcons adapt to changed ecological conditions resulting from global warming. The Gyrfalcon has a long historical association with mankind. Captive propagation now provides many Gyrfalcons for . This technique could provide offspring for replenishing wild populations, should the need arise. Wild Gyrfalcons use various, manmade structures for nesting, and this habit offers a possibility to establish pairs in areas with a good food supply but no natural nest-sites. Received 17 February 2011, accepted 31 May 2011.

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CADE, T. J. 2011. Biological traits of the Gyrfalcon (Falco rusticolus) in relation to climate change. Pages 33–44 in R. T. Watson, T. J. Cade, M. Fuller, G. Hunt, and E. Potapov (Eds.). Gyrfalcons and Ptarmigan in a Changing World, Volume I. , Boise, , USA. http://dx.doi. org/ 10.4080/gpcw.2011.0104

Key words: Gyrfalcon, ptarmigan, distribution, abundance, arctic ecology, climate change.

LONG ADMIRED FOR its variable rang- northern proto-Gyrfalcons in a refugium from ing from nearly white to dusky gray and for its the southern sakers. Subsequent redistributions prowess as a hunter of grouse, the Gyrfalcon and isolations of gyr populations provided (Falco rusticolus) is the northern-most diurnal opportunities for local differentiations of white raptor with a circumpolar breeding distribution and dark birds respectively in refugia located restricted to subarctic and arctic zones from in northwestern Greenland and Ellesmere about 55ºN to 82ºN. Although some Gyrfal- Land and in coastal Labrador, while the ances- cons move southward into north temperate tral gray gyrs remained in temporally shifting zones in winter, others, particularly adult south of the main ice masses in Eura- males, remain in subarctic and low arctic sia and (Johansen 1956, Palmer regions wherever suitable prey such as ptarmi- 1988, Flann 2003, Cade 2006). Following the gan and marine birds can be found. Adult end of the last glaciations Gyrfalcons with females and juveniles wintering farther south these geographically differentiated colors have switch from ptarmigan to waterfowl, shore- come together and interbred but have not yet birds, corvids, pigeons, and other grouse such achieved panmixia, thus producing the confus- as Sharp-tailed (Tympanuchus phasianellus) ing mix of plumage variations we see today. and Sage Grouse ( urophasianus) in North America (Cade et al. 1998, Booms et These hypotheses based on morphology and al. 2008). historical biogeography appear to be consistent with some of the emerging findings of molec- ular phylogenetics of the Hierofalco group of PHYLOGENETIC RELATIONSHIPS AND ORIGIN falcons, and of other avian species, but not The Gyrfalcon likely evolved from a Saker with all of this work. For example, Wink et al. Falcon (Falco cherrug) or saker-like ancestor (2004) found genetic distances of 0.4% to after biotas became established follow- 2.0% among the four falcon species in Hiero- ing the first major glaciation at the Pliocene- falco and estimated that this modest degree of Pleistocene boundary around 2 million years differentiation would have occurred in a period BP, although another idea is that this split from 200,000 to 1,000,000 years BP. They between the two kinds of falcons did not occur further noted that in other families of birds until after the last glaciation around 10,000 such small genetic differences indicate taxo- years BP (Nittinger et al. 2005, Potapov and nomic distinction at no more than the level of Sale 2005, Cade 2006). As first proposed by . Also, estimates of species diver- Johansen (1956), the Gyrfalcon may have sep- gence times for other groups of birds, based on arated from its ancestral stock at the end of the molecular systematics and “clocks,” indicate long Mindel-Riss interglacial period some 200 that most recent speciation occurred from 1 to to 300,000 years BP, when extensive steppes 5 million years ago (early Pleistocene to connected with arctic grasslands, Pliocene) and that isolations allowing falcons and many other open land- caused by glaciation occurred too recently to scape organisms to extend their ranges north- account for speciation events (Klicka and Zink ward. Renewed glaciations then separated the 1997). These findings are in line with the view

34 –GYRFALCON IN RELATION TO CLIMATE CHANGE – that the Gyrfalcon and saker are allopatric sub- eyries in West Greenland has revealed some species of one polytypic species or “allo- interesting details about these changes over the species” of one Hierofalco superspecies [see past 2,500 years (Burnham et al. 2009). also Potapov and Sale (2005) for historical views of O. Kleinschmidt, A. Kots, and R. RECENT CHANGES IN DISTRIBUTION Meinertzhagen]. Historically recent changes in the southern The more recent idea that the proto-Gyrfalcon limits of the Gyrfalcon’s breeding range may became isolated from the ancestral saker only be associated with lesser climatic events since after the last major glaciation some 10,000 the last major glaciation, such as the “Little Ice years BP (Potapov and Sale 2005) has been Age” from ca. 1300 to 1870 A.D. Two nesting supported by recent molecular phylogenetic pairs of Gyrfalcons were reported from the studies, which also emphasize the small degree of southern Labrador, a “black” pair and of genetic differentiation between Gyrfalcons young at the mouth of the Bras d’Or River, and sakers (Nittinger et al. 2005, 2007, Daw- , at 51º28’N in 1833 (specimens col- nay et al. 2007, Johnson et al. 2007). The “out- lected there were the basis of Audubon’s of-” hypothesis of Nittinger et al. that a famous painting and description of the Black North African (Falco biarmi- Gyrfalcon Falco labradora, Audubon 1834); a cus) population was the ancestral source for all “light colored” pair also nested “for many of the Hierofalco “species” seems plausible, years” in the late 1800s at Henley Harbour, but the further suggestion that the Gyrfalcon 52º01’N (Townsend and Allen 1907, Todd and Saker Falcon were independently derived 1963). Based on several government reports from ancestral Lanner stock makes no sense (e.g., Goudie et al. 1993), currently Gyrfalcons from a comparison of phenotypic similarities apparently do not breed farther south in and differences within the Hierofalco group or Labrador than Harp Lake at about 55ºN inland from zoogeographic considerations of their from Hopedale. There is also a recent record of breeding ranges. These genetic studies confirm nesting on Long Island along the eastern shore the close relatedness of the saker and Gyrfal- of Hudson Bay at 54º53’N (Brodeur et al. con with detected genetic differentiation no 1995). The two nesting records from extreme greater than that of subspecies in many other southern Labrador may represent the last of a polytypic species of birds. The fact that none breeding group of Gyrfalcons that had of the molecular genetic studies has so far extended their range down the Labrador coast shown a complete separation of the Saker Fal- during the Little Ice Age, when arctic condi- con and Gyrfalcon indicates that they should tions existed further south than they do today. probably be considered allopatric subspecies None of the published maps, including the one of one polytypic species. in Booms et al. (2008), correctly depicts the southern boundary of the gyr’s breeding range Whatever the real history of these phylogenetic on the Ungava Peninsula. events was, there is little doubt that the gyr has experienced repeated expansions, contractions, Similar events may have occurred in other and fragmentations of its breeding range during parts of the breeding range. On the Kamchatka the Pleistocene glaciations, and its past adapt- Peninsula, where historical and even current ability to survive these changes suggests that it records are somewhat confusing, (Dement’ev will have considerable ability to adjust to the 1951, 1960, Ellis et al. 1992, Potapov and Sale current climate changes that are upon us, unless 2005, Lobkov et al. 2007), local people they become too rapid and severe owing to reported Gyrfalcons nesting on coastal cliffs anthropogenic influences. The radiocarbon dat- on the southeastern coast at the mouths of ing of accumulated guano piles at Gyrfalcon rivers at 51º09’ N and 51º29’N in the late

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1800s (Dybowski 1883). Today the falcons The situation in southern and western Green- apparently do not breed regularly, if at all, land is not well documented either. Basically south of the Kronotskiye Peninsula at ca. 54º all that we know is that prior to Salomonsen’s to 55ºN and may be decreasing northward monograph (1951), the Gyrfalcon was consid- toward the Koryak District (57º42’N), where ered to be a widely distributed breeder in the gyr is, or has been, a relatively common South Greenland and along the west coast nester (Lobkov et al. 2007). north to Umanaq (Uummannaq) district at ca. 71ºN. Most of Salomonsen’s records date prior Gyrfalcons also no longer nest in the Koman- to 1910 (Hagerup 1891, Winge 1898, and dorskiye Islands (55ºN), where Stejneger Muller 1906 all reported gyrs nesting com- (1885) found white birds breeding in the monly in South Greenland). Since 1981 Falk 1880s. There is also one outlying record of a and Møller (1988, 2009) have carried out nest found in 1924 on Matuwa Island in the annual surveys for Peregrine Falcons (Falco Kurils at 48º04’N (Yamashina 1931, Potpov peregrinus) in South Greenland. They have and Sale 2005). This record has been ques- never found evidence of Gyrfalcons nesting in tioned, but an adult specimen exists. their study areas, which are inland where pere- grines are common and ptarmigan are few. Gyrfalcons in the Ural Mountains, with a According to K. Falk (pers. comm.) the gyrs north-south axis of 2,500 km reaching from are outer coastal in distribution, and a few low arctic to north temperate latitudes, provide pairs still breed at widely scattered locations another uncertain example. Sabaneev (1874) up the west coast at least as far as Nuuk described observations (first hand and second (Godthab). How far north on the west coast hand) of Gyrfalcons nesting in the middle this apparent reduction of breeders occurs is Urals at ca. 56ºN, where none occur at the not known, but Gyrfalcons appear to be breed- present time. Dement’ev (1951) and Ellis et al. ing less frequently than they were 30 to 40 (1992) accepted these reports as valid, but they years ago in both the Kangerlussuaq (Søndre have been severely criticized by Portenko Strømfjord) region and the Uummannaq Bay (1937) and Potapov and Sale (2005), who sug- region (Burnham et al. 2005, Burnham 2007). gested that they were based on misidentified Just when the apparent reduction in the num- Saker Falcons. A key might be whether or not ber of Gyrfalcons in South and West Green- ptarmigan occurred in this region in sufficient land began and how much it is related to abundance to support breeding Gyrfalcons. natural climatic changes or to more recent Currently, a few gyrs nest in the polar region anthropogenic impacts on climate and related of the northern Urals at ca. 66ºN (Potapov and ecological changes remains to be puzzled out, Sale 2005). If the southern reports are correct, if possible, from the sparse records of the past. this situation would represent another major Again, it would be important to know what northward retraction of the breeding range associated changes have taken place in the dis- since the end of the Little Ice Age. tribution and abundance of ptarmigan and . This whole region requires more Recently Sorokin (2009) reported Gyrfalcons study. nesting in 2005 and 2008 in a tall tree nest of the Imperial (Aquila heliaca) in a habi- There seems to be no sign of a northward tat of bogs and lakes with scattered islands of retraction of the breeding range in Norway, forest at 59ºN in the Kondo-Alymskaya Wet- where nesters still occupy the historical range lands east of the Urals. This location is only at least as far south as 58º–59ºN (Tømmeraas about 3º of latitude north of the nearest nesting 1994). The other southern region requiring Saker Falcons. renewed investigation is northern British

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Columbia, where a dozen nest sites have been on gyr populations will be mediated through recorded in alpine terrain below 60ºN (south of impacts on ptarmigan distribution and abun- 58ºN in one case) in the not too distant past dance. Even so, gyrs do use alternative prey in (Campbell et al. 1990). some situations—notably seabirds (alcids and ), waterfowl and shorebirds, such as the Snow Bunting (Plectrophenax TO A COLD CLIMATE nivalis) and Lapland Longspur (Calcarius lap- The Gyrfalcon is the largest of the true falcons ponicus), hares (Lepus spp) and Ground Squir- (fat-free males typically range from 1,000 to rels (Spermophilus undulatus), and 1,400 g, females from 1,250 to 2,000 g), and and during peak years. Also, the avian this large body size is no doubt advantageous predators of microtine rodents such as the for existence in a cold climate owing to the Long-tailed Jaeger (Stercorarius longicaudus), reduced heat loss related to the lesser surface to Parasitic Jaeger (Stercorarius parasiticus), volume ratio of its body compared to that of Short-eared (Asio flammeus), and even smaller birds. It also has dense downy plumage the Northern Harrier (Circus cyaneus) can be with large, fluffy aftershafts on the contour significant in the diet in some years (Cade feathers and partially feathered tarsometatarsi, 1960, Cade et al. 1998, Potapov and Sale 2005, additional features that confer bioenergetic and Booms et al. 2008). thermoregulatory advantages for existence in the cold. Under good feeding conditions, the Under climate change some of these species gyr can accumulate 200 to 300 or more grams could become important substitutes, if ptarmi- of body fat, and it can temporarily store that gan populations undergo serious declines or much food in its crop (Cade 1999). These shifts in distribution and abundance away from energy stores permit the gyr to seek shelter historical falcon nesting habitats. For example, from severe storms and high winds and to ground might start emerging earlier remain inactive for several days on end without in spring and increase in number as permafrost metabolizing any of its muscle mass for energy. melts and drier, ice-free soils become more Although no physiological study has been per- available to burrowing rodents. These condi- formed, observations on the lethargic behavior tions are also likely to favor the Red-backed of captive birds (Palmer 1988) under certain (Myodes rutilus) and the Singing Vole conditions suggest that the Gyrfalcon may also (Microtus miurus), but the wetland Brown drop its body temperature a few degrees centi- (Lemmus trimucronatus) and Tundra grade and reduce its metabolic rate during these Vole (Microtus oeconomus) can be expected to periods when it cannot hunt for food. decline. Likewise, increase in shrubby vegeta- tion (especially willows) and extension of spruce trees northward could promote perma- FOOD AND TROPHIC RELATIONS nent establishment of the Snowshoe The gyr feeds mainly on ptarmigan (Lagopus (Lepus americana) in the Low Arctic of North spp), often 50 to 90% of annual diet, and the America. An instance of the invasion of this breeding and wintering distributions of the hare into the Colville River of Arctic Gyrfalcon parallel very closely those of the occurred in the 1990s (T. Swem pers. Rock Ptarmigan (Lagopus muta) and the Wil- comm.). Changes in the distribution and abun- low Ptarmigan (Lagopus lagopus). This close dance of seabirds, waterfowl and shorebirds, trophic relationship has evidently existed and passerines—as well as ptarmigan—can all throughout the Pleistocene Epoch. It seems be expected under a continuing regime of likely that any major impact of climate change

37 –CADE – global warming, sometimes to the benefit of ing pairs of falcons are reduced below the the Gyrfalcon, sometimes not (Hamer 2010). number of available nest sites, because the Gyrfalcon has a limited ability to switch to alternate prey, particularly early in the breed- BREEDING BIOLOGY ing cycle when females must build up their Historically the gyr has been the earliest breed- nutritional reserves for reproduction (see N. ing raptor in the Arctic, laying in April (even Barichello, this conference). On the other late March) to mid-May, depending on lati- hand, in years of exceptional abundance of tude, and close in timing to the Common ptarmigan, some pairs of gyrs will occupy Raven ( corax), another early breeder, marginal nest-sites that in most years would the old stick nests of which often provide gyrs not be used. Such a situation occurred on the with needed nesting substrates. Early breeding Colville River in arctic Alaska in1990 when 26 seems necessitated in part because the gyr has pairs nested in a region that usually holds only a long reproductive cycle of ca. 160–180 days eight to 14 pairs (T. Swem pers. comm.). from establishment of nesting territory to inde- pendence of fledged young in mid- to late In most gyr populations the establishment of August, shortly before winter begins. Breeding breeding pairs and the onset of laying are also seems to be timed so that nestlings fledge closely tied to the late winter and early spring during the period of peak availability of young, abundance of ptarmigan. This dependence inexperienced prey, especially ptarmigan (see appears to apply even to pairs that switch later Potapov and Sale 2005, Figure 7.1). It is in the breeding cycle to feeding on seabirds or unclear just how climate change, especially on waterfowl and shorebirds. Gyrfalcons nest- warming, may change the breeding phenology ing in the Thule region of northwestern Green- of the gyr relative to that of its prey, but con- land begin laying in May at about the time trary to expectation, Gyrfalcons in Ter- Dovekies (Alle alle) first arrive on their nesting ritory are now breeding later than they used to cliffs. Several authors have noted this corre- do (see D. Mossop, this conference). spondence in the time falcons lay and of seabirds (Dement’ev and Gyrfalcons usually nest on cliffs in a location Gortchakovskaya 1945, Salomonsen 1951, well protected from weather, often on a high Cade et al. 1998, Potapov and Sale 2005, wall of rock but also on some remarkably low Burnham 2007), but the critical point is that rocks only a few meters above the ground. In the female gyr has probably spent a month or some areas, especially in , they also use two on her nesting territory building her old stick nests of other birds in trees, particu- energy reserves for reproduction prior to the larly those of Common Ravens but also , arrival of the seabirds, which are late nesters. Rough-legged ( lagopus), and a Ptarmigan and hares are about the only prey few other species. Some cliff sites can only be available at that time. In the autumn during occupied when stick nests are present. As old their dispersal and migration from the breeding stick nests are ephemeral, gyrs can only grounds, young Gyrfalcons depend mainly on occupy tree nesting sites and some cliffs when juvenile ptarmigan, microtine rodents, and a suitable stick nest is present, and this fact juvenile birds for food (Cade et al. probably accounts for the many one-time or 1998, Booms et al. 2008). two-time nest occupancies that characterize the Gyrfalcon, as compared to the peregrine. Another aspect of breeding is that like most avian predators in the Arctic (jaegers, , In many parts of the range, nest sites appear to and diurnal raptors with the notable exception set an upper limit to nesting population size, of the Peregrine Falcon), the Gyrfalcon’s but in years of low ptarmigan numbers breed- ptarmigan prey base fluctuates or cycles dras-

38 –GYRFALCON IN RELATION TO CLIMATE CHANGE – tically in numbers from year to year, so that in it has been suggested that the increasing num- peak periods of food abundance, a maximum ber of Peregrine Falcons may be forcing gyrs to number of pairs attempt to breed (but success abandon territories by interference competition still depends mainly on good weather); over nest-sites or by feeding so persistently on whereas, in years of low prey abundance fewer ptarmigan during the breeding season that their pairs attempt to breed. Under climate change numbers surviving to early spring of the fol- the 10-year population cycles of ptarmigan and lowing year are below the level that induces hares and the 3- to 4-year cycles of microtine gyrs to begin laying (Burnham 2007). The less rodents appear to be damping with lower peaks diverse and abundant prey base in Greenland and less regularity between high and low years compared to northern Alaska could be a factor (e.g., Gilg et al. this conference). Whether tipping the competitive advantage to the Pere- these population changes will persist and what grine Falcon in Greenland; whereas, the richer they portend for predators needs more study, prey base in Alaska may mitigate competition but it seems clear that until now the Gyrfalcon for food between these two species, and an has successfully adjusted to the cyclic and abundance of nest-sites reduces competition for irregular fluctuations in density of its principal suitable places to breed. prey by capitalizing on the occasional peak years of reproduction to counter the low pro- Alternatively, the gyrs may be abandoning ductivity of sparser years. nesting sites for reasons other than competi- tion, such as overall change in the distribution and abundance of prey species, and then the INTERSPECIFIC RELATIONS peregrines take over the abandoned nest-sites. WITH OTHER RAPTORS Nelson (1969) reported an example of such a Among the diurnal raptors regularly breeding situation in which Prairie Falcons (Falco mex- in the Arctic, only the Gyrfalcon and Rough- icanus) took over the abandoned eyries of legged Hawk are arctic specialists; the pere- Peregrine Falcons during a prolonged period grine, (Aquila chrysaetos), and of drought and DDT use in the Pacific North- White-tailed Sea Eagle (Haliaeetus albicilla) west of North America in the 1940s to 1960s. (also the raven) are generalists with extensive breeding distributions in other regions. The lat- As previously discussed, the Gyrfalcon and ter are likely to be winners as climate change Saker Falcon are disjunct, allopatric species or modifies the ecological conditions of the Arc- subspecies of two closely related groups of fal- tic, while the former are more likely to be los- cons. In captivity their gametes are fully com- ers (Hamer 2010). patible, producing not only F1 hybrids that produce fertile offspring by backcrossing with The peregrine and Gyrfalcon are potential com- either parental species but also fertile to petitors for nesting sites and for food hybrid crossings through successive genera- (Salomonsen 1951, Cade 1960). In arctic tions (Heidenreich et al. 1993, M. Heidenreich Alaska where gyrs and peregrines often nest in pers. comm., N. and associates unpub- the same localities and sometimes together on lished data). If climate change should alter the same cliffs, it appeared that the gyr domi- biomes in such a way that breeding popula- nated the peregrine in interactions over nest- tions of Gyrfalcons and Saker Falcons eventu- sites because of its larger size and earlier ally come together, there is little doubt that breeding season (Cade 1960, White and Cade interbreeding would occur between the two 1971). In West Greenland, where nesting pere- with extensive introgression of genes. Such grines have increased dramatically during the hybridization might actually help Gyrfalcons past 50 years and Gyrfalcons have decreased or adapt to the changing ecological conditions disappeared progressively from south to north, brought on by global warming. It is likely that

39 –CADE – hybridization between gyrs and sakers has upon to maintain the protocols and studbook already occurred one or more times during the data required for proper genetic management Pleistocene, as evidenced by the intermediate of their breeding stock. Consideration should characteristics of the “Altai Falcon” in central be given to the acquisition of new, wild breed- Asia (see Potapov and Sale 2005 for an ing stock to counter inbreeding problems, par- extended discussion; also, Eastham 2000). ticularly in the case of any conservation breeding projects that may develop for future reintroduction and restocking purposes. RELATIONS WITH HUMANITY Like the Peregrine Falcon, the Gyrfalcon has Furthermore, despite the CITES treaty, which had a long history of association with mankind provides a framework for international trade in in the sport of falconry (Dement’ev 1960, wildlife, inconsistencies among nations and Potapov and Sale 2005). It has always been the burdensome regulations in various countries most prized of all the hunting falcons used in discourage and in some cases prohibit trade. falconry because of its large size and rarity— Government has the responsibility to help and great beauty—and gyrs were often maintain the health and fitness of captive Gyr- exchanged as gifts among potentates. The falcon populations to insure that captive bred species is still sought after today, and both falcons remain a viable alternative to wild legal and illegal trade occur, mainly to the birds, both for the sport of falconry and for Middle East. Captive propagation now pro- conservation. Current policies and rules favor vides large numbers of gyrs for falconry, a the commercial propagators and make it proven technique that could also be used for extremely difficult for private, nonprofit breed- re-establishing wild populations, should the ers and scientists to export and import birds need arise. needed to maintain the genetic viability of their breeding stock. A problem that needs international considera- tion is that the number of wild founders of the Wild Gyrfalcons are also known to use various worldwide stock was quite manmade structures for nesting, and this habit small, almost certainly fewer than 40 birds, offers a possibility to establish nesting pairs in some of which were closely related to each areas with a good food supply but no natural other and perhaps only half of which were pro- nest-sites, as is currently being done for the lific breeders. This situation has led to much Saker Falcon in Mongolia (see A. Dixon this inbreeding, especially within the breeding conference; also A. Østlyngen and K. Johansen stock of individual propagators, despite the this conference; V. Morozov this conference). several thousand falcons that have been com- Currently many such areas exist throughout mercially produced for falconry in the past 40 the circumpolar arctic regions, and more may years. A reduction in body size and egg size be created as global warming progresses. has become evident in the more recent gener- ations of falcons; reproductive problems and CONCLUSION other signs of inbreeding depression are also appearing. Line breeding for specific colors It seems likely that the aspect of the Gyrfalcon’s (extreme white, extreme dark) and large body life history that will be most vulnerable to the size has exacerbated inbreeding. Unfortu- impacts of climate change is its dependence on nately, there has been limited exchange of ptarmigan as its main source of food in the early unrelated individuals among propagators, and stages of the annual breeding cycle before eggs some commercial breeders cannot be relied are laid and young hatch. Even though gyr pop-

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ulations in several kinds of situations can shift LITERATURE CITED effectively to feeding on seabirds, waterfowl and shorebirds, or on other species of birds and AUDUBON, J. J. 1834. The Birds of America, mammals after their eggs hatch, there appears vol. 2, plate 196. Published by the author, to be no situation in which they can breed suc- London, UK. cessfully in the absence of substantial numbers BOOMS, T. L., T. J. CADE, AND N. J. CLUM. of ptarmigan at the time females are storing 2008. Gyrfalcon (Falco rusticolus). In A. energy for egg production. Arctic hares, or pos- Poole (Ed.). The Birds of North America sibly lemmings, under some circumstances Online. Ithaca: Cornell Lab of Ornithology; where they occur in sufficient numbers, might New York, USA. Retrieved from The Birds be an adequate substitute for ptarmigan, or even of North America Online database: http:// seabirds wintering on polynyas within the for- bna/birds.cornell.edu.bnaproxy.birds. aging range of nesting gyrs; but I know of no cornell. edu/bna/species/114 case in which such situations have actually been BRODEUR, S., F. MORNEAU, R. DECARIE, J. observed to occur. The Gyrfalcons nesting on DESGRANGES, AND J. NEGRO. 1995. South- Ellesmere Island and surrounding islands ern extension of the breeding range of the should be investigated from this standpoint in Gyrfalcon, Falco rusticolus, in eastern the early season (see Cade and 2011, Muir North America. Arctic 48:94–95. and Bird 1984). BURNHAM, K. K. 2007. Inter- and intraspecific variation of breeding biology, movements, A longer and warmer arctic summer might and genotype in Peregrine Falcon Falco offer Gyrfalcons some opportunities to adjust peregrinus and Gyrfalcon F. rusticolus pop- their annual cycle to new sources of food dur- ulations in Greenland. Doctoral Disserta- ing their pre-laying period. The falcons might tion. Wolfson College, University of adjust by delaying their reproductive cycle Oxford, Oxford, UK. until after adequate prey arrive on their territo- BURNHAM, K., W. A. BURNHAM, AND I. NEW- ries, an adjustment made possible by the later TON. 2009. Gyrfalcon Falco rusticolus fall freeze-up, allowing time to complete their post-glacial colonization and extreme long- long breeding cycle. Conversely, prey such as term use of nest-sites in Greenland. Ibis seabirds, waterfowl, shorebirds, even ground 151:514–522. squirrels, may start appearing on the scene BURNHAM, W., K. K. BURNHAM, AND T. J. much earlier than previously, providing a sup- CADE. 2005. Past and present assessments plement to whatever ptarmigan are still avail- of bird life at Uummannaq District, West able. A wintertime shortage of ptarmigan in the Greenland. Dansk Ornithologisk Forenings Arctic and Subarctic also may force more Gyr- Tidsskrift 99:196–208. falcons to migrate into temperate zones during CADE, T. J. 1960. Ecology of the Peregrine and winter. In other words, the Gyrfalcon may Gyrfalcon populations in Alaska. Univer- have to become more like the arctic-breeding sity of California Publications in Zoology Peregrine Falcon in the characteristics of its 63:151–290. annual cycle—breeding later in relation to the CADE, T. J. 1999. The Gyrfalcon’s adaptations arrival of suitable prey, feeding on a wider for survival in arctic regions. Pages 55–68 assortment of prey species, and migrating far- in E. Ford. Gyrfalcon. John Murray, Lon- ther away from its breeding territories in win- don, UK. ter. Such changes might, however, lead to CADE, T. J. 2006. The Gyrfalcon. Auk increased competition between these two 123:920–923. species of falcons. These are all intriguing pos- CADE, T. J., AND D. M. BIRD. 2011. Seasonal sibilities that will need to be anticipated and changes in diet of Gyrfalcons nesting at monitored carefully in the coming decades. Ellesmere Island and other high Arctic

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MULLER, R. 1906. Vildet og Jagten i Sydgrøn- SOROKIN, A. G. 2009. Kondo-Alymskaya land. H. Hagerups Boghandel, Copen- ornithological anomaly, Russia. Raptors hagen, Denmark. Conservation 15:90–96. [In Russian and NELSON, M. W. 1969. The status of the Pere- English.] grine Falcon in the . STEJNEGER, L. 1885. Results of ornithological Pages 61–72 in J. J. Hickey (Ed.), Pere- explorations in the Commander Islands and grine Falcon Populations, their Biology and in Kamtschatka. Bulletin of the United Decline. University of Wisconsin Press, States National Museum 29:1–382. Madison, Wisconsin, USA. TODD, W.E.C. 1963. Birds of the Labrador NITTINGER, F., A. GAMAUF, W. PINSKER, M. Peninsula and adjacent areas: A distribu- WINK, AND E. HARING. 2007. Phylogeogra- tional list. University of Toronto Press, phy and population structure of the Saker Toronto, Canada. Falcon (Falco cherrug) and the influence TØMMERAAS, P. J. 1993. The status of Gyrfal- of hybridization: Mitochondrial and con Falco rusticolus research in northern microsatellite data. Molecular Ecology Fennoscandia 1992. Fauna Norvegica 16:1497–1517. Series C, Cinclus 16:75–82. NITTINGER, F., E. HARING, W. PINSKER, M. TOWNSEND, C. W., AND G. M. ALLEN. 1907. WINK, AND A. GAMAUF. 2005. Out of Birds of Labrador. Proceedings of the Africa? Phylogenetic relationships between Boston Society for Natural History Falco biarmicus and other Hierofalcons 33(7):277–428. (Aves: ). Journal of Zoological WHITE, C. M., AND T. J. CADE. 1971. Cliff- Systematics and Evolutionary Research nesting raptors and ravens along the 43:321–331. Colville River in arctic Alaska. Living Bird PALMER, R. S. 1988. Handbook of North 10:107–150. American Birds, vol. 5. Yale University WINGE, H. 1898. Grønland’s Fugle. Med- Press, New Haven, Connecticut, USA. delelser om Grønland. 21(1):1–316. PORTENKO, L. A. 1937. Birds of the Non-Polar WINK, M., H. SAUER-GÜRTH, D. ELLIS, AND R. Parts of the Northern Urals. Academy of KENWARD. 2004. Phylogenetic relation- Sciences, Leningrad, Russia. [In Russian.] ships among the Hierofalco complex POTAPOV, E, AND R. SALE. 2005. The Gyrfal- (Saker-, Gyr-, Lanner-, Laggar Falcon). con. T. & A. D. Poyser, UK, and Yale Uni- Pages 499–504 in R. D. Chancellor and B.- versity Press, USA. U. Meyburg (Eds.). Raptors Worldwide: SABANEEV, L. P. 1874. Vertebrates of the mid- Proceedings of the VI World Conference on dle Urals and their Geographical Distribu- Birds of Prey and Owls. MME/WWGBP, tion in the Perm and Orenburg Districts. St. Budapest, Hungary, and Berlin, Germany. Petersburg, Russia. [In Russian.] YAMASHINA, Y. 1931. Die Vogel der Kurilen. SALOMONSEN, F. 1951. Grønlands Fugle, vol. Journal für Ornithologie 79:491–541. 3. Copenhagen, Denmark.

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