摘要:

The feeding sites of European Wigeon Anas penelope are always close to water. Initial studies suggest that this is primarily an anti‐predator behaviour rather than a requirement for drinking and bathing. Vigilance and flock‐size measurements at varying distances from water support this hypothesis. However, birds will feed away from water if grass biomass is greater further away. The end of the shooting season also causes birds to feed further away from wa

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02736.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Experiments were carried out on wild and hand‐reared Egyptian Vultures to investigate the origins of the stone‐throwing this species uses to break into Ostrich eggs. There was no evidence of cultural transmission for stone‐throwing through copying experienced birds. A naïve captive‐reared bird threw stones once an Ostrich egg had been linked with a food reward. The origins of aimed stone‐throwing are probably related to the unaimed throwing of small eggs, since the actions are similar, and all tested birds strongly preferred to throw rounded or egg‐like stones, rather than jagged ones, at

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02737.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Twenty‐nine Red Kites, that were tagged as nestlings in Wales, bred for the first time at 2–7 years old (mean 3–6). A minimum of 41% of tagged young had entered the breeding population by the 7th year. Individuals moved up to 22 km between birthplace and breeding place and, having bred, most stayed in the same locality from year to year. No differences in these various respects were found between the sexes, though two long movements by territorial birds both involved females. Annual survival of adult breeders was estimated at aroun

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02738.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A close fit was found between the number of years since European settlement and the call and dive‐rates of Red‐tailed Hawks. Call‐rates were highest in the most recently settled

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02739.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

This paper describes the distribution and behaviour of passerine birds within 1 km of Peregrine FalconFalco peregrinuseyries in western Greenland. Passerine populations were censused in 1983 around six cliffs occupied by nesting Peregrines and at six sites on the open tundra, and in 1984 at two unoccupied sites suitable for Peregrine nesting.Four passerine species accounted for over 90% of birds seen. Within 400 m of Peregrine occupied cliffs, three species, Lapland LongspurCalcarius lapponicus. Northern WheatearOenanthe oenanthe, and Common RedpollCarduelisflammea, were found in lower than average abundance while the fourth, Snow BuntingPlectrophenax nivalis, was found in increased abundance. Our indirect tests suggest that Peregrine presence, rather than direct predation, was responsible for the distributions of the first three species. The Snow Bunting, however, behaviourally adapts to Peregrine presence in order to exploit nesting habitat available at the cliff base.These results contrast strongly with those reported by other Arctic workers, where increased abundances of potential prey were observed in close proximity to nesting Peregrines.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02740.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Breeding success of 176 Tawny Eagle pairs nesting on basalt (4724 km2– 92 pairs) and kalahari sand (9876 km2– 84 pairs) was monitored from 1973 to 1984 in Hwange National Park, Zimbabwe. Flat‐topped trees were preferred for nesting but kalahari sand pairs used round‐crowned trees more often, probably due to tree availability. Mean inter‐nest distances on both biomes were significantly different (3–5 km on basalt, 59 km on kalahari sand). Clutch size and frequency of one‐egg clutches in both biomes were similar and many more one‐egg clutches were laid in the drier period of the study (1979–1984). There was no correlation between laying date and breeding success. More basalt pairs laid synchronously, probably due to the smaller inter‐nest distances. Breeding success in both biomes was similar and significantly more chicks were reared during 1973–1978 than during 1979–1984 (wet and dry periods, respectively). Some districts produced more chicks than others, suggesting good and marginal areas within both biomes. The greater inter‐nest distances and ability to breed successfully in round‐crowned trees by kalahari sand Tawny Eagles resulted in a similar number of chicks reared per breeding attempt as basalt pairs, in spite of the lower primary

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02741.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The mating system and mate choice of Tengmalm's Owls were studied in relation to population fluctuations of the staple food (voles) for seven years in western Finland. Three age classes of owls were differentiated: first‐year, second‐year and older owls. Despite a surplus of males, 11 % of them showed simultaneous bigyny in peak vole years. The mean distance between primary and secondary nests was 1158 m, and usually there was a free nest‐box between the two nests. Because primary nests produced more fledglings than secondary ones and secondary nests produced fewer fledglings than simultaneous or even eight‐days‐later monogamous nests, this bigyny could be best explained by the ‘deception’ hypothesis.In successive biandry, females deserted their first brood when young were still in the nest, thereby transferring the burden of raising the young to their males. The tendency of assortative mating by age (more yearling x yearling and + 2‐year‐old ×+ 2‐year‐old pairs than expected by chance) showed that females chose older males whe

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02742.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02743.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

During a three‐year study of 82 pairs of MoorhensGallinula chloropus,seasonal reproductive success (SRS) varied greatly between pairs. Pairs on big territories had a higher SRS than pairs on small territories, probably because clutch survival was higher on big territories. Pairs that began breeding early had a higher SRS than pairs that began late because early breeders laid larger clutches and could attempt more broods. Pairs with heavy males had bigger territories and began breeding earlier than pairs with light males. Heavy males therefore had a higher SRS than light males. Female weight did not affect territory size, timing of breeding, or female SRS. Assuming SRS to be a good predictor of lifetime reproductive success, selection should favour heavy males but not heavy females. Male Moorhens are significantly heavier than female Moorhens. Finally, pairs with breeding experience had a higher SRS than pairs without, because they had bigger territories and began breeding earlier. However, males in inexperienced pairs were not lighter than males in experienced pairs, so it is not clear why they defended smaller territories or laid late

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02744.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A study was carried out in northeastern Venezuela to determine whether or not shorebirds feed at night in tropical environments. Results show that some Neotropical residents and Nearctic winter migrants feed during darkness. During daylight, Black‐winged StiltsHimantopus himantopus, mexicanusgroup, were predominantly visual foragers (75% attempts were pecking), performing a tactile type of feeding technique (immersion of the whole head and portion of the neck while searching for food through soft mud) on other occasions. During night‐time, they were almost equally visual (pecking) and tactile (multiple scythelike sweeps) foragers. Greater and Lesser YellowlegsTringa melanoleucaandT. flavipesforaged visually during daylight and tactilely (sidesweeping) at night. Short‐billed DowitchersLimnodromus griseuswere tactile feeders (probers) both by day and by night while Semipalmated PloversCharadrius semipalmatusduring daylight and at night and Wilson's PloversC. tvilsoniaby night were sight feeders (peckers). Prey abundance was higher at night than during daylight. Black‐winged Stilts and yellowlegs seemed to feed at night on food items at least partly different from those they fed upon during d

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1989.tb02745.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY