摘要:

The social organization and behaviour of the HoatzinOpisthocomus hoazin, a cooperatively‐breeding folivorous bird, was studied in the central plains(llanos)of Venezuela. In this area Hoatzins nested in communal social units of two to eight individuals. Units were usually composed of a breeding pair and up to six helpers at the nest. Helpers, usually offspring retained from the previous years' nesting, aided in all breeding activities of their social unit except egg production. On the study site, Hoatzin units defended extremely small, all‐purpose territories along watercourses during the rainy (breeding) season, but migrated up to 2 km to areas with permanent water during the dry season. Nesting extended from early May to October. Nest and egg measurements and growth rates of young are provided. Nesting success was low (27%), primarily due to predation byCebus olivaceusand several other species. Annual survival of adults and young was high. Young did not breed during their first year; 90% of yearlings remained on their natal territories as helpers. Females appear to be the dispersing sex. The results are discussed in relation to previous work on the Hoatzin. The demography of the study population fits the criteria for several recent theories regarding the evolution of cooperative breeding in bi

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02714.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Transepidermal water loss was studied in nestlings, fledglings and adults of the xerophylic Zebra FinchPoephila guttata.Nestlings lose little water (2–4 ppm/0–5 cm2/h) through the skin as compared to adults (60–70 ppm/0–5 cm2/h). Light and electron microscopic examination of the skin sections of both age classes revealed an abundance of lipids in the form of vacuoles and large multigranular bodies in the epidermis of nestlings, but few such lipid bodies in the epidermis of adults. Some of the disc‐like contents of granular bodies appear to be extruded into the intercellular spaces. Based on earlier studies with mammals and reptiles, it is concluded that epidermal lipids are the basis of the integumentary permeability barrier in

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02715.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Differential predation of eggs of Glaucous‐winged GullsLarus glaucescenswas studied on Mitlenatch Island, British Columbia. The predation of single eggs from 3‐egg clutches by conspecifics and Northwestern CrowsCorvus caurinuswas recorded to assess whether the predators selected eggs at random or showed a preference for a specific egg in the laying sequence. It was found that small and light‐coloured eggs, characteristically the last‐laid egg in the clutch, were taken significantly more often than the other two eggs in the clutch. As chicks derived from this third egg are least likely to fledge because of their small size and the effects of asynchronous hatching, the lightness of the third egg is adaptive in that it helps to focus attention on the sm

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02716.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A method is described for the identification of arthropod fragments in the faeces of gamebird chicks. The method of collection and preparation of faecal samples and the identification of commonly occurring arthropod parts is described. The use of diagnostic parts, specific to certain groups, enables the method to be used quantitatively as well as qualitatively. Photographs of the major diagnostic features are provided.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02717.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Energy expenditures of Salvin's PrionsPachyptila vittata salvini, Blue PetrelsHalobaena caeruleaand Great‐winged PetrelsPterodroma macropteraduring growth were estimated from measurements of oxygen consumption. Total energy expended during growth was calculated to be 6877 kJ and 10206 kJ for the smaller Salvin's Prions and Blue Petrels, respectively, and 22697 kJ for the larger Great‐winged Petrels. A further 2390 kJ, 3067 kJ and 11801 kJ, respectively, was calculated to be accumulated as body tissue. Food requirements for growth, estimated from energy requirements, diets and assimilation efficiencies were estimated to amount to 1519 g and 932 g for Salvin's Prions and Blue Petrels, respectively, and 4577 g for Great‐winged Pe

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02718.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02719.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Great Spotted Cuckoo nestlings were shown, after some days in the nest, to have begging calls that differed depending on whether they were being reared by Magpies or Carrion Crows. They also produced calls of a pitch and repetition rate that implied a high level of hunger.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02720.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In a breeding population of Red Grouse the ratio of cocks to hens was about 2:1. Cocks with hens had bigger territories and richer feeding sites than unmated cocks. Despite this, the size of a cock's territory was inversely related to the level of nitrogen in his food. The idea that this was because cocks defend a territory just big enough to meet the pair's food requirements seemed inapplicable, since territories were much bigger than this. In addition, it was inferred that hens took longer to choose a cock on a part of the area that had relatively poor feeding sites. Whether hens chose the cock or his territory was uncertain, but both probably played a part.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02721.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02722.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1988.tb02723.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY