摘要:

SummarySummer bird populations were studied in ten sites: two heathlands, two maritime pinePinus pinasterplantations, one, four, seven and 13‐year‐old eucalyptEucalyptus globulusplantations, one climax oakQuercus roburwoodland, and a farmland area in northwestern Galicia, Spain. The farmland and oak wood contained the greatest number of species (24 and 17 respectively) while the one and four‐year‐old eucalypt stands contained the fewest species (four and six respectively). Avian density was highest in the oak wood (93 birds/ 10 ha) and lowest in a heathland site, the four and one‐year‐old eucalypt stands (26,13, and seven bird/10 ha respectively). The wren was the most widespread and dominant species occurring in all study areas except the one‐year‐old eucalypt stand. Mean bird species diversity for the four eucalypt stands was significantly lower than mean bird species diversity for the other wooded habitats. The avian communities of the heathlands, maritime pine and eucalypt plantations, in contrast to the oak wood and farmland, show an excessively high dominance of one species. Using avian dominance as a biological index of habitat perturbation suggests that over half the landscape (4000 km2) in northwestern Galicia is suffering from chronic stress. The newest stress to the avifauna in a long history of land exploitation by man is the importation and cultivation on grand scale of eucalypts. Balancing this tendency, traditional, small‐scale farming on the mountainous terrain leads to the development of many tiny parcels whose average size is 0.28 ha; this in turn creates much ‘edge’ in hedgerow which serves to maintain a relatively rich avian species

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03736.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryMale Chaffinches share no more songs with territorial neighbours than would be expected by chance, suggesting that some song learning occurs before young birds set up their territories. Hand‐reared birds are capable of learning song both in their first spring and in the previous summer one young bird produced a good copy of a song which he had only heard as a nestling and fledgling eight months previously. While song learning involves accurate copying of individual elements, the variation in number in elements in a phrase and the temporal pattern of singing shown by hand‐reared birds were similar to that of wild birds rather than being influenced by the tutor ta

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03737.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryWe describe 12 visual and six acoustical displays of Black‐collared Barbets, all associated with interactions of these sexually monomorphic barbets in greeting ceremonies and in antiphonal duets. Certain of the displays, e. g., bill directing, smooth posture and chatter calls largely are associated with multiple‐barbet interactions and greeting ceremonies involving more than two barbets, and seem to represent purely agonistic displays. Other displays, most notably the bobbing and floating flight displays, and thetyawcall, are associated with preduet greeting ceremonies involving the presumed pair. In every case duets were performed by a presumed pair, following a greeting ceremony and visual displays accompany the duetting, which usually becomes precisely synchronized after the initial few notes. Four to 17 notes of each of two types, a usually lower pitched, short and mainly double type A note that introduces most duets, and a higher pitched, usually single, clear type B note that often terminates the duet. Variation in the notes and in their tempos within duets suggests no clearly defined temporal indicators for achieving, maintaining, and concluding the duets. The A and B notes cannot yet be assigned to one or other sex and similarity in form and development of the notes, from notes of greeting ceremonies, suggests the possibility that under some circumstances a bird of one sex may be able to deliver notes of either type. The duets are delivered from singing posts within the group's (or pair's) territory and usually only one duet is uttered from a site before the birds shift to another singing post. The duetting is compared with that of other barbets and appears to be among the best synchronized and most precise in the family. Comparisons with non‐barbet duetting species are difficult because of the special habits and ecology of the barbets and uncertainty as to the sexual rôle of the du

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03738.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

SummaryHummingbirds in the tropical rainforests of southwestern Costa Rica face intense competition from stingless beesTrigonathat steal nectar from hummingbird flowers. Here we document both interference and exploitative competition between bees and hummingbirds at scarlet, hummingbird pollinated flowers ofPassiflora vitifolia. Aggressive stingless bees prevented Long‐tailed Hermit HummingbirdsPhaethornis superciliosusfrom feeding at nearly one‐third of the passion flowers approached. In exclusion experiments, bees and hummingbirds each removed most of the nectar from treated flowers. Experimental exclusion of bees also increased hummingbird use of both natural and artificial flow

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03739.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03740.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03741.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03742.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03743.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03744.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1982.tb03745.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY