Tom J. Cade’s research while affiliated with Cornell University and other places

DEVOLVIENDO A FALCO FEMORALIS A LOS ESTADOS UNIDOS Se liberaron volantones de Falco femoralis criados en cautiverio a lo largo de las planicies costeras del sur de Texas (839 aves de 21 sitios durante 1993–2004) y en el desierto de Chihuahua del oeste de Texas (637 aves de 11 sitios durante 2002–2011) y del sur de Nuevo México (337 aves de 10 sitios durante 2006–2012). Las liberaciones en la costa de Texas produjeron dos poblaciones que anidaron: 15–18 pares cerca de Brownsville y 15 pares en dos islas cerca de Rockport. El hábitat de esta área se compone de una extensa sabana abierta, lo que representa la condición ancestral de casi toda la región. Actualmente se encuentra casi completamente dominada por tierras de labranza y matorrales; este último alberga a Bubo virginianus, uno de los mayores depredadores de halcones. Por el contrario, las liberaciones en el desierto de Chihuahua no fueron exitosas en el establecimiento de poblaciones silvestres. Aunque se encontraron 8–10 pares en el oeste de Texas en 2009, para el 2011 sólo se registró un par y no se encontró ninguno en 2012, como consecuencia aparente de una sequía severa. Una sola pareja documentada en Nuevo México en 2011 estuvo asociada con la alimentación artificial de aves de presa. Concluimos que la conservación y la expansión de poblaciones de F. femoralis en las planicies costeras de Texas requerirán de la protección y el manejo de los territorios de cría existentes, y de la creación y manejo de sabanas libres de matorrales. La sequía persistente, la reducción de las poblaciones de presas y las altas tasas de mortalidad debidas a la depredación por parte de rapaces parecen impedir el restablecimiento de poblaciones de F. femoralis en el oeste de Texas o Nuevo México.

Largest of the true falcons (Falco spp.), the Gyrfalcon (Falco rusticolus) is the north-ernmost diurnal raptor with a circumpolar breeding distribution restricted to subarctic and arctic zones between 55º and 82º N. Some Gyrfalcons 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 species (Lagopus 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 birds and mammals 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 hares 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-falcon 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 Peregrine Falcon (Falco peregrinus) are potential competitors for nesting sites and food. In West Greenland, 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 Saker Falcon (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 falconry. 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. 33 LONG ADMIRED FOR its variable plumage rang-ing from nearly white to dusky gray and for its prowess as a hunter of grouse, the Gyrfalcon (Falco rusticolus) is the northern-most diurnal raptor with a circumpolar breeding distribution restricted to subarctic and arctic zones from about 55ºN to 82ºN. Although some Gyrfal-cons move southward into north temperate zones in winter, others, particularly adult males, remain in subarctic and low arctic regions wherever suitable prey such as ptarmi-gan and marine birds can be found. Adult females and juveniles wintering farther south switch from ptarmigan to waterfowl, shore-birds, corvids, pigeons, and other grouse such as Sharp-tailed (Tympanuchus phasianellus) and Sage Grouse (Centrocercus urophasianus) in North America (Cade et al. 1998, Booms et al. 2008).

A BSTRACT.—Gyrfalcons (Falco rusticolus) breeding in the High Arctic Canadian Islands and in northern Greenland have available to them widely scattered nesting sites on cliffs throughout much of this region, but their food resources are limited to four principal species, Rock Ptarmigan (Lagopus muta), Snow Bunting (Plectrophenax nivalis), Collared Lemming (Dicrostonyx torquatus), and Arctic Hare (Lepus arctica), with seabirds, waterfowl, and shorebirds playing a role in some localities. The distribution and abundance of these principal prey are highly variable in time and space, and consequently the serviceability of eyries is unpredictable and largely determined by the abundance of food in a particular year. Most Gyrfalcon populations depend on an abundance of ptarmigan (Lagopus spp.) for their food during the critical period of establishing a pairbond and laying eggs in late winter (mid-April and May in the High Arctic). Ptarmigan are now rather sparse in the High Arctic and apparently seldom build up to numbers that can support Gyrfalcon reproduction without supplementation by other prey. Where the Collared Lemming occurs and reaches “peak” numbers in some years, it apparently serves as a substitute, abetted by whatever ptarmigan are available. Early spring flocks of male Snow Buntings may also help. Whether or not Gyrfalcons can exploit adult hares effectively at this time remains a question that needs study. At the time female gyrs are incubating eggs in late May and June, the leverets of Arctic Hare become available, and Gyrfalcons utilize them heavily where they are common. Lemmings, if they survive into the summer, and leverets can support falcon reproduction through the nestling period into August. During migration in late August and on into September and October, the juvenile falcons feed heavily on the large flocks of young Snow Buntings. In special situations, large breeding colonies of Dovekies (Alle alle) provide the bulk of food during the nestling period of the falcons. The principal herbivores included in these trophic relationships—ptarmigan, lemming, and hare—fluctuate drastically in numbers from year to year and may have “cyclic” peaks ranging in interval from four to 11 years depending on species and locale. The correspondence of peak years in two or more of these species may strongly influence successful reproduction by Gyrfalcons and may account for the spectacular fall movements of falcons formerly reported in NE Greenland. Evidence is growing that the amplitude of these “cycles” has been decreasing and their periodicity increasing or breaking down under the influence of climate change. Gyrfalcon populations might well decline under these circumstances. The strong dependence of the High Arctic gyrs on maritime and marine birds for their winter food could also be jeopardized if the arctic sea

ABSTRACT The scientific evidence that California condors (Gymnogyps californianus) are frequently sickened and killed by lead poisoning from spent ammunition supports the conclusion that current levels of lead exposure are too high to allow reintroduced condors to develop self-sustaining populations in the wild in Arizona and, by inference, in California. The evidence for lead poisoning and its source comes from the following sorts of data: 1) 18 clinical necropsies revealing high levels of lead in body tissues and (or) presence of lead shotgun pellets and bullet fragments in digestive tracts; 2) moribund condors showing crop paralysis and impending starvation with toxic levels of lead in their blood; 3) widespread lead exposure among free-flying condors, many with clinically exposed or acute levels; 4) temporal and spatial correlations between big game hunting seasons and elevated lead levels in condors; and 5) lead isotope ratios from exposed condors showing close similarity to isotope ratios of ammunition lead but isotope ratios in less exposed condors being similar to environmental background sources, which are different from ammunition lead. Simple population models reveal harmful demographic impacts of unnatural mortality from lead on population trajectories of reintroduced condors. Recent innovations in the manufacture of nonlead shotgun pellets and bullets with superior ballistics now provide for a simple solution to the problem of lead ingestion by condors, many other species of wildlife, and human beings: substitute nontoxic forms of ammunition for traditional lead-based ammunition. The substitution of nontoxic ammunition would be highly efficacious for hunting, economically feasible, and the right thing to do.