摘要:

SUMMARYThe winter foraging behaviour of Willow TitParus montanuss, Coal TitP. aterand Crested TitP. cristatuswas studied in several spruce‐dominated, coniferous forest areas in which either Willow Tit alone, Willow Tit and Coal Tit, or all three species together were present. In the areas where Crested Tits were absent, Willow Tits foraged significantly more often in the outermost parts of spruce branches and less frequently on the parts of branches closer to the trunk, than in the area in which Crested Tits were present. In the area in which all three species were present, the same change in foraging pattern of Willow Tits was found in mixed flocks in which Crested Tits were lacking. The foraging pattern of Coal Tits was unaffected by the presence of members of either or both the other two tit species. It is suggested that the expansion of the feeding niche of Willow Tit in the absence of Crested Tit is a result of ecological release, due to a reduction in the degree of interspecific competitio

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06770.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYActivity cycles of non‐breeding Adelie Penguins were investigated at Cape Bird, Antarctica. There was continuous light during the observation period, but none the less regular fluctuations of light intensity and temperature were maintained. The penguins had no single period of rest, but were active throughout the 24 hours. However, there were statistically significant diurnal variations in the levels of certain activities among non‐breeders, with an overall reduction in activity‐levels in the middle of the day, especially on warm midsummer afternoons. It is suggested that this cyclic activity minimum may be associated with the low heat tolerance of Adelie Pen

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06771.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYA survey of 40 species of 14 genera of North American wood‐warblers (Parulidae) reveals that the head‐scratching method employed is surprisingly stable within species. The experiments by Nice&Schantz (1959a, b) induced some normally overwing head‐scratchers to scratch the head under the wing. It is suggested that this was because their leg rings became caught in secondaries, making normal overwing head‐scratching impossible. A few exceptional head‐scratching patterns under different conditions invariably involved normally overwing head‐scratchers employing the underwing method, and a few species head‐scratch under the wing as nestlings but change to overwing before fledging. In all, 31 species appear to be normally overwing head‐scratchers, seven are underwing head‐scratchers, one species uses both methods and one remains uncertain. There is no evidence for lateral preference in either head‐scratching method, and head‐scratching is only loosely linked sequentially to preening. The functional significance of head‐scratching may be related to blockage of the eustachian tube, or to cleaning and oiling the feathers. Avian head‐scratching is more difficult to homologize with mammalian head‐scratching than others have considered it to be, but all evidence suggests that within birds underwing head‐scratching is phylogenetically primitive. In wood‐warblers, the head‐scratching method does not correlate with taxonomy. However, ground‐dwelling wood‐warblers tend to scratch the head under the wing and arboreal wood‐warblers over the wing. This correlation provides the first strong clue to the functional significance of the differ

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06772.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYThe Harrier‐HawksPolyboroidesspp. and Crane HawkGeranospiza caerulescenshave legs capable of flexing backward as well as forward at the intertarsal joint. This is evidently adaptive to their habit of extracting prey from crevices using the feet. The structure and properties of the intertarsal joint have been investigated using an alcoholic specimen ofP. typusand skeletons ofP. typusandG. caerulescens; specimens ofCircus cayaneus(alcoholic) andC. aeruginosus(skeleton) were used for comparison. Increased mobility of the joint extends to medial‐lateral swing as well as flexion; the faculty for backward flexion appears to be somewhat offset by some loss of forward flexion. The tibiotarsus, tarsometatarsus and the ligaments and menisci of the intertarsal joint are described and figured. No significant differences in musculature were found. The most obvious difference betweenCircuson the one hand, andPolyboroidesandGeranospizaon the other is the extreme narrowness of the joint in the latter two genera. This is probably the most important factor permitting increased joint mobility. The possible significance of other structural features observed is also discussed, and related adaptations of the distal tarsometatarsus and foot are pointed out. It is concluded that the resemblances of the hind limbs of these two genera are not strong evidence of phylogenetic relations

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06773.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYWhite‐winged ChoughsCorcorax melanorhamphuslive in groups of 2–20 birds that nest communally. Most of the study population (82%) was composed of groups of 4–8 individuals. The oldest male in each group appears to perform a ‘linchpin’ role in group cohesion, and groups tend to disintegrate if he dies or leaves. Polygyny is shown to occur, and it is thought that some 15% of clutches are due to two females laying in the same nest. Progeny tend to stay in their natal group rather than dispersing. They help to rear subsequent offspring. All group members may help to build the nest and to incubate, brood, guard, clean and feed the young (both in and out of the nest). No correlation was found between group size and the rate of feeding young in the nest. From 186 nesting attempts, the average production was 1–4 birds of which only 16% survived to adulthood (= 4 y. o.).Besides their nesting activities, White‐winged Choughs have a form of communal defence; they, also, roost, forage, drink, bathe, dust, and roost together. It is concluded that the association into groups provides the adaptive advantage of a buffer against periodic fluctuations in available food– the youngest (= smallest investme

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06774.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYA comparison of morphological characters shows thatPicoides tridactylusis more markedly sexually dimorphic thanDendrocopus leucotos, D. majororD. minor. This is correlated with intersexual differences in foraging behaviour inP. tridactylus, lacking in theDendrocopusspp. Apparently as a consequence, the sexes are able to share winter territories amongP. tridactylusbut not amongD. majororD. minor; conclusive observations ofD. leucotoswere not possible. It is suggested that these differences may reflect the distributional history of the species, and the extent of interspecific competition.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06775.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06776.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06777.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06778.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1978.tb06779.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY