摘要:

The effect of various characteristics of Canada GooseBranta canadensisfemales and clutch size on their nest defence intensity during incubation was studied in the field during five nesting seasons. Nests were approached by a human, and the leaving distance was measured. Risk‐taking in post‐encounter behaviour was categorized at three levels. Nesting success was significantly associated with nest tenacity, a variable derived from leaving distance, but not with post‐encounter behaviour. Nest tenacity, as well as post‐encounter behaviour, differed significantly between individuals. Intensity of post‐encounter behaviour, but not nest tenacity, increased with increasing age of the female. Nest tenacity, standardized over the incubation period, increased with increasing clutch size, but post‐encounter behaviour intensity did not. None of the nest defence variables was correlated with the structural size of the female. Nest tenacity, but not post‐encounter behaviour intensity, increased during incubation. Nest tenacity did not differ between early and late breeders, but post‐encounter behaviour was more intense in late breeders. There was no evidence of positive reinforcement of nest defence through repeated visits. Nest defence did not differ between lakes, lake types or nest site types, nor was it affected by the distance to the nearest neighbouring nest. The results supported several of the predictions extracted from parental in

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01076.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Membership of three permanent breeding colonies of Zebra FinchesTaeniopygia guttatastudied in farmland changed continually due to arrival and departure of birds from distant colonies. Sixty‐six percent of adults stayed for less than 1 month, and many that stayed longer disappeared for extended periods. Over 78% of adults captured were hatched in other colonies and only 23% made a breeding attempt in their natal colony. There was no sex‐biased natal dispersal or philopatry, but there were sex differences in the timing of dispersal. Sex ratios at the end of parental care were variable and may depend on food resources. Adult ratios were slightly male‐biased. Annual losses of adults ranged from 72 to 82% across colonies, but mortalities and dispersal were heavily confounded by high adult mobility. The oldest bird was more than 5 years old. A total of 67% of young were lost between fledging and nutritional independence at 35 days of age, and only 20% of fledglings survived to day 80, the age of first breeding. Artificial supplies of seed at baited walk‐in traps prolonged the stay of dispersing adults from other colonies, enhanced the survivorship of young hatched in the colony and possibly affected the secondary sex ratio. In this southeast part of their Australia‐wide distribution, Zebra Finch populations appear to be highly mobile over a very large home range with extensive free interchange of members among a number of permanent breeding colonies. High mobility may be adaptive for exploiting patches of seed and water in a highly erratic en

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01077.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Crested TitParus cristatusyoung from first broods dispersed 1 week later if they were born in small isolated pine plots (‘habitat fragments’) compared with individuals in a large pine forest (‘continuous habitat’). This delay in dispersal was caused by an extended period between fledging and dispersal. In second broods, the delay was even longer due to the interbrood interval being 9 days longer in habitat fragments. As nestlings in habitat fragments had a lower body‐mass, and age at dispersal was negatively correlated with nestling body‐mass within each nest, the postponed dispersal from fragments might be explained partly by a lower body‐mass. Alternatively, postponed dispersal from fragments could result from a barrier effect caused by reluctance to cross inhospitable habitat.Immigration by young from first broods into habitat fragments was delayed by approximately 3 weeks, and proportionally more second brood emigrants were recovered in this type of habitat. These results are in agreement with the hypothesis that fragments are second‐choice habitat. Early immigrants into continuous habitat had a higher probability of settlement in winter flocks compared with late ones, independent of condition or age. Therefore, Crested Tits born in habitat fragments probably have a lower chance of settling in first

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01078.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Thirteen active and 14 old Archbold's BowerbirdArchboldia papuensisnests were studied in Tari Gap, Southern Highlands, Papua New Guinea. Clutch size was one egg. At two nests, only one‐parent nest attendance was observed. Incubation and nestling periods were considerably longer and nestling growth slower than in other bowerbird species, possibly reflecting adaptation to a colder environment depauperate in insects. Of 382 identified nestling meals, 71% were exclusively fruit (14 spp. identified) and 29% were animal. Of 112 animal meals, 30% were skinks (Reptilia), 28% were small arthropods, 17% were beetles and the remainder (25%) were larger insects, pieces of nestling birds and unidentified items. Most active nests were built adjacent to older nests and the significance of this is discusse

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01079.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The clutch sizes of the passerines of Israel and the Cape Province, South Africa, which lie at similar latitudinal range, were compared. Mean clutch sizes in Israel and the Cape Province are 4.09 and 2.87, respectively. Mean clutch size of Israeli migrants is larger than that of residents (4.45 and 3.93, respectively), but no such difference exists in the Cape Province.It is suggested that the larger clutch size in Israel is a result of two factors: (1) the higher proportion of wintering birds in Israel in comparison with the Cape Province and the presence of many transients there which may compete with resident birds and cause high winter mortality among them and (2) a higher proportion of migrants in the Israel avifauna, which suffer heavy losses during their trans‐Saharan migration in comparison with Cape Province migrants, which travel shorter routes. The resulting reduced competition for food during the breeding season in Israel enables passerines there to lay larger clutches as predicted by Ashmole (1963) and Ricklefs (1980

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01080.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Two small southern African bustards, the Black‐winged KorhaanEupodotis afra afraand the White‐winged KorhaanE. a. afraoides, have long been treated as conspecific. However, differences in their habitats, plumage, morphometrics, displays and vocalizations of males, mitochondrial DNA restriction fragment length polymorphisms and, possibly, social systems strongly suggest that they are distinct spec

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01081.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

I observed the natural process of family break‐up in 13 families of Black KitesMilvus migransand five families of Red KitesM. milvusin which fledglings had been individually marked. In other broods, I performed experiments which modified the parental investment fledglings received by supplementing nests of both species with food or transferring Black Kite chicks to nests with younger or older chicks of the same species.The time of family break‐up in the Black Kite is mainly an offspring decision which is not affected by an artificial increase of parental investment. The duration of the post‐fledging period was not increased in Black Kites that were given supplementary food. Chicks transferred to nests with a younger chick did not extend the post‐fledging period, nor did chicks transferred to nests with an older chick shorten the post‐fledging period. In Red Kites, parental investment seemed to have more influence on the timing of the family break‐up. Red Kite adults invested less as parents than did Black Kites during the post‐fledging dependence period, and in nests where supplementary food was given, Red Kite fledglings stayed attached for a

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01082.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Physical condition of migrating Steppe BuzzardsButeo buteo vulpinuswas determined during spring migration at Elat, southern Israel, 1984–1988. An index based on measurements of body mass, wing‐length and culmen was used to estimate fat content, based on fat extraction from nine buzzards. In addition, hydration condition was measured in 1988 and moult was checked in 1985–1988. More immatures (1001) than adults (459) were trapped, and a greater percentage of immatures (19.8%) than adults (8.4%) was retrapped during the same season. Adults had significantly greater fat reserves (4.5% of body mass) than immatures (3.8%). Most adults were in some stage of interrupted moult: however, active primary moult was noted only in immatures (10%). These findings suggest that different age groups use different migration strategies. Most of the buzzards trapped in this study could not have completed their entire migration using only stored fat: thus, hunting was probably necessary to replenish their energy reserves. No indication of water stress was found in the spring of

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01083.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The scavenging activities of Greater Yellow‐headed VulturesCathartes melambrotuswere studied in the Amacayacu National Park, Colombia. This species is the most abundant vulture in the area and is usually the first species to locate a carcass, both in open clearings and inside the forest. The birds use olfaction to locate food. Vultures located 63% of provided carcasses, while mammalian scavengers found only 5%. Greater Yellow‐headed Vultures were displaced when feeding by both Turkey VulturesCathartes auraand King VulturesSarcorhamphus p

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01084.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Time budgets of free‐living chicks of Arctic TernsSterna paradisaeaand Common Terns S.hirundothroughout development are presented with special reference to changes in time allocation when growth rate varies. Chicks of both species were inactive most of the time observed (87%). Time allocated to the different behaviours changed during development and was generally better correlated with body mass than age. Slower growing nestlings were brooded more and allocated more time to quiescence and less time to locomotion, preening, begging and attacking (the latter two significant only for the Arctic Tern). The energetic implications of variation in time budgets with age and growth rate were considered. Parental brooding resulted in an average energy saving of nearly 40% of an individual nestling's thermoregulatory costs. Whereas thermoregulatory costs remained nearly unchanged in Arctic Tern chicks, these were negatively correlated with growth rate in Common Terns. Tentatively, we estimated a 30% reduction in a nestling's total energy requirement for a 50% reduction in average growth rate for both specie

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1994.tb01085.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY