Charles H. Trost

EGG RECOGNITION IN YELLOW-BILLED AND BLACK-BILLED MAGPIES IN THE ABSENCE OF INTERSPECIFIC PARASITISM: IMPLICATIONS FOR PARASITE-HOST COEVOLUTION

Abstract Yellow-billed Magpies (Pica nuttalli) ejected 100% of nonmimetic eggs placed in their nests despite such behavior having no detectable present day benefits. They are not currently parasitized, nor is there any evidence of a recently extinct brood parasite. Furthermore, there was no molecular evidence of conspecific parasitism, and Yellow-billed Magpies accepted eight of nine conspecific eggs transferred between nests, so recognition would rarely be of benefit if conspecific parasitism occurred. Thus, we suggest that egg recognition in Yellow-billed Magpies is a plesiomorphic trait, a primitive character inherited from a remote ancestor, its nearest relative, the Black-billed Magpie (Pica pica). The latter suffers from parasitism by Great Spotted Cuckoos (Clamator glandarius) in Eurasia and displays rejection behavior throughout Europe in populations that are allopatric and sympatric with this cuckoo. As would be expected if Yellow-billed Magpies inherited rejection behavior from the Black-billed Magpie, or the common ancestor of both species, we found that North American Black-billed Magpies also have well developed egg recognition despite being unaffected by interspecific parasitism. The long-term retention of host defenses as is indicated by magpies has major implications for the coevolutionary interactions between brood parasites and their hosts.

Sex determination of the whooping crane by analysis of vocalizations

Much work has been done with Whooping Cranes (Grus americana), officially listed as an endangered species under the Endangered Species Act of 1973. However, very few studies have been concerned with Whooping Crane vocalizations. This study was initiated as a result of observations by Dr. Rod Drewien of the University of Idaho. In his work with the experimental, cross-fostered population of Whooping Cranes that migrates between Grays Lake, Idaho and Bosque de1 Apache National Wildlife Refuge, New Mexico, Drewien noticed that the pitch of the Guard Call may differ between sexes in the Whooping Cranes (R. Drewien, pers. comm.). No reliable sexual dimorphism exists in Whooping Cranes, and at the time of Drewien’s observations the preferred method of determining the sex of Whooping Cranes was by karyotyping of mitotic cells from developing feathers. Because birds must be captured, this method is impractical. Potentially, call analysis could provide an easier method of determining the sex of Whooping Cranes (R. Drewien, pers. comm.). In addition, significant differences between sexes exist in pitch of the Guard Call in the closely related Greater Sandhill Crane (Grus canadensis) (Weekley 1985). Differences in calls between sexes have also been found in Manx Shearwaters (Pujinus pujinus) (Brooke 1978). Archibald (1977) had shown sex-related frequency differences in the Unison Call of Whooping Cranes, and pairs also exhibited sex-specific postures during this call (Archibald 1977, pers. observ.). Unison Calls, however, are performed only by pair-bonded, adult cranes and, in addition, are rarely observed in wild Whooping Cranes (T. Stehn, pers. comm.; R. Drewien, pers. comm., pers. observ.). Unison Calls, therefore, do not provide a reliable means of sex determination for adults, and no means of sex determination for subadults. Alternatively, Guard Calls are produced by all nonjuvenile Whooping Cranes, whether paired or not, are given by sub-adults as young as one year of age (pers. observ.), are heard very frequently, and are easily induced without great distress to the cranes (T. Stehn, pers. comm.; R. Drewien, pers. comm., pers. observ.). In addition, Guard Calls are loud and, unlike lower

Predators, risks and context for mobbing and alarm calls in Black-billed Magpies.

Abstract Black-billed magpie, Pica pica hudsonia, mobbing and alarm calls were recorded for each of several different predator contexts. These were analysed spectrographically to determine whether the callers used temporal variation to communicate (1) the nature of the danger, (2) the identity of the predator and (3) the risks involved in actions resulting from alertness to the presence of the predator (e.g. fleeing or mobbing). The results support the notion that magpies vary call syllable length to give recipients information about the nature of the danger and to respond to a predator in an appropriate manner. Playback experiments were conducted using recordings of the separate call types as stimuli. The aim of the playback experiments was to determine whether one form of call elicits a more intense reaction from recipients than another call. It was found that magpies responded to calls with longer syllables by approaching the speaker while their response to calls with shorter syllables was aversive.

Self-advertisement: relations to dominance in black-billed magpies

Etude, chez Pica pica hudsonia, du comportement antipredateur. Cette etude est realisee en prenant en compte le statut social des individus ayant ce comportement dans les volees

Migrant Shorebird Habitat Use and the Influence of Water Level at American Falls Reservoir, Idaho

AssTRAcr-Shorebirds migrating at American Falls Reservoir, Snake River, Idaho, were counted in fall from 1986 to 1988 to determine their habitat use and the influence of water level changes. Reservoir water levels changed within and between seasons, sometimes changing the habitat type at specific sites. Shorebirds concentrated on mudflats, whereas sandy, clay, and boulder beaches, and bedrock supported very low numbers of individuals and species. Shorebirds were excluded from some important mudflats in early migration in 1986 because of flooding by high water, and densities drastically dropped after a rise in water flooded some mudflats later in the season. Shorebird numbers were correlated with water drawdown in 1986. There were equal or higher numbers of shorebirds at the large mudflat site in 1987 and 1988 when water drawdown caused the shoreline to recede 15,000 to 20,000 m versus 1986 when the shoreline receded 3200 m. This study shows that man-made reservoirs can provide important staging areas for migrating shorebirds. Mudflats should be made available on reservoirs in the intermountain western United States from late June through October.