摘要:

Phylloscopus hainanusis a distinctive new species in the family Sylviidae. The species is endemic to Hainan Island, China, where it is restricted to tropical forest in mountains above 600 m. The most distinctive plumage features are the rather deep yellow underparts and the mainly white outer rectrices.

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02803.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The first Tertiary cockatoo or any psittaciform from Australia is recorded from an incomplete rostrum from the Riversleigh deposits of northwestern Queensland, Australia. It is placed in the extant genusCacatuabut cannot be diagnosed at the specific level. This cockatoo was probably similar in size to the modernC. roseicapilla, with a short, unspecialized crest and probably white plumage. The rostrum is useful in studies of the systematics of parrots. Rostral characters support some traditional subdivisions of the order, while suggesting that others warrant re‐examinatio

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02804.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Weights of food loads brought back to the colony by 26 ShagsPhalacrocorax aristotelisrearing chicks were determined using the water‐offloading procedure. Loads consisted almost entirely of lesser sandeelsAmmodytes marinus.Load size was extremely variable, ranging from 8 to 208 g with a mean load weight of 106 g. Data on foraging behaviour collected concurrently demonstrated that Shags brought back heavier loads when they were feeding farther away from the colony and when brood biomass was larger. These two variables together explained 70.3% of the variation in load size. We postulate that adults had already digested their own food requirements by the time they arrived back at the nest, and the contents of the loads were therefore primarily for the young. On 67% of trips, Shags caught, on average, more than one fish per dive. This estimate ignores the food requirements of the adult, and therefore true prey‐capture rates must have been hig

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02805.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Food provisioning to chicks of Little EgretEgretta garzettain a colony at Ligagneau in the Camargue, southern France, was measured using electronic nest balances. Both pair members supplied food to the chicks, and each performed three to five alternating foraging trips.The loading rate during the first trip of the day (1.09 g/min) was more than three times as high as that during later trips (0.32 g/min) and accounted for 20% of the daily amount of food delivered. This food was collected while the birds were feeding in dense aggregations on mosquitofish which had become temporarily concentrated due to hypoxic conditions overnight in the surrounding marsh. Later in the day, when this concentrated food source was no longer available, the birds fed solitarily.The total amount of food delivered per day remained constant at 385 g as chick age increased from 10 to 20 days. Given the observed loading rates, 385 g is near the maximum amount of food the pair can deliver during a 16.5‐h daylight period when they forage continuously throughout the day but only one parent at a time. This indicates that a time constraint limits the amount of food delivered to a brood during this stage of the breeding cycle. Given this time constraint, the total amount of food delivered per day would have been reduced by 25% if the birds had not been able to benefit from the concentrations of mosquitofish during the early morning.Breeding success was significantly higher at Ligagneau (3.25 chicks/nest) than in other Camargue colonies (2.69 chicks/nest). In addition, post‐fledging survival of chicks with a low rank in the brood hierarchy was probably better at Ligagneau than elsewhere in the Camargue. We attribute this elevated reproductive output at Ligagneau to the exceptionally large amount of food collected by egrets during the early morning aggregations, which were probably formed in response to predictable concentrations of mosquitofish in the permanent marshes surrounding this colony. Such aggregations were rarely observed in the temporary marshes surrounding the other colonies, probably because the occurrence and location of fish concentrations are difficult to predict in this habitat due to rapidly falling water lev

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02806.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Red‐breasted MergansersMergus serratorwere counted in the river North Esk, Scotland, and on the sea nearby, 1987–1990. Pairs arrived at the river estuary from early winter, but the main influx to freshwater took place in late April and in May, when breeding pairs dispersed far upriver. Females began incubation from late May. Most young hatched in July and fledged by late September. Males left the river in June and congregated at an offshore moulting site, their numbers peaking in August, and dispersed rapidly in September.Breeding density and total duckling production decreased with increasing distance upstream, decreasing river width and increasing gradient and elevation. The total number of breeding pairs and their distribution on the river were similar from year to year, despite variable numbers killed, suggesting a stable breeding population near the upper limit the habitat would support in those years. It also suggested that killing mergansers in April was an ineffective way to reduce the population. The spatial variation in merganser breeding density was not correlated with the density of their main spring food, parr of salmonSalmo salar, but could have been related to its availability.The production of well‐grown ducklings varied annually and was inversely correlated with river flow during the main period of hatch. It is argued that Red‐breasted Mergansers breed late in the year because the hatching of ducklings in July coincides with an abundance of their food, large aquatic invertebrates and tiny juveni

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02807.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

This paper describes the diet of young LammergeiersGypaetus barbatusduring the nesting period on the island of Corsica. From 1985 to 1990, food items were collected from 10 nests after the young had fledged. These nests were from five territories where the potential food supply was estimated using a range of ‘large mammal’ counts. Feathers, bones and isolated hooves were used to identify prey. For each nest, the minimal number of food portions was quantified, ignoring material that provided no food value. The diet consisted mainly of limb extremities of domestic ungulates (c. 36% by number of portions of sheep and goat; 33% of cattle, mostly calves). Pigs, both wild and domestic, yielded c. 16% of the items. Where present on the territory, mouflon occurred frequently in nests (c. 12% of items). Birds and small mammals were scarce in the diet. For three territories, samples varied less among years than among territories. There was a strong association between the diet of the young and the food available in the territories. We examined the possible links between known 20th century changes in stock rearing activities and the Corsican Lammergeier's d

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02808.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Annual survival of breeding female SparrowhawksAccipiter nisuswas estimated by a capture‐recapture procedure in three different areas, Eskdale and Annandale in southern Scotland and Rockingham Forest in east‐central England.In Eskdale, where the breeding population remained fairly stable during a 19‐year study, annual survival averaged 59% (s.e. = 4%). In Annandale, where the breeding population declined during a 10‐year study, annual survival averaged 66% (s.e. = 4%). In Rockingham, where the breeding population increased during an 11‐year study, annual survival averaged 72% (s.e. = 4%). In this area, survival declined during the study as numbers rose. The apparent density‐dependence in survival was therefore confounded with a time trend.In all three areas, annual variations in survival were negatively related to the number of rain days during October‐April, but the relationship was significant only in Eskdale. This area had the longest run of data and the greatest variation in the number of winter rain days. The relationship with rain days could partly account for the differences in mean survival between areas, with lowest survival in the wettest area and highest survival

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02809.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The results of a long‐term capture‐mark‐recapture ringing programme carried out on a coastal population of breeding RedshanksTringa totanusbetween 1974 and 1988 are presented.Both sexes were equally likely to be recaptured in subsequent years, as were birds captured for the first time compared with those that had been captured previously. Older birds were more frequently recaptured than were young birds. There was no significant difference in male and female adult survival rates, with a mean of 72% of females and 75% of males surviving each year.The breeding population fluctuated annually with estimated breeding densities of 122–285 pairs per km2. Variation in breeding numbers (males), but not survival, was partially attributable to winter air temp

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02810.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The fact that one cannot kill a bird twice makes it very difficult to determine the relative contributions of fat and non‐fat components to increases in body mass before migratory flights in individual birds. Knowing the relative contributions of these components is of obvious energetic interest since fat yields about eight times as much energy as fat‐free muscle tissue. Several recent studies have failed to demonstrate convincingly, due to flaws in their analyses, that fat‐free mass in addition to fat is accumulated before long‐distance flights. We point out that regressions of fat or the non‐fat component on total body mass cannot yield reliable estimates of the composition of individual mass changes in view of inter‐individual variation in structural size, reserve levels or timing of storage. We suggest that studies over time of synchronous populations or marked individuals will give better answers. A re‐analysis of published data indicates the widespread existence of fat‐free tissue deposition during migration, whereas in some species fat alone explained the increase in total body mass. Larger species tend to incorporate a relatively higher proportion of non‐fat components when increasing in mass. However, the comparative data set is not yet of sufficient quality to allow general statements on why, and to what extent in different individuals and species, non‐fat tissue in addition to fat is deposited before take‐off

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02811.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Extrinsic factors that play a role in the control of clutch‐size in Blue TitsParus caeruleuswere investigated. The disruption of ovarian follicular growth, and hence the cessation of egg‐laying, is caused by a stimulus generated by eggs present in the nest. The timing of this disruption varies among females during the laying period and may happen as late as after the laying of the eighth egg of the clutch; the larger the clutch, the later the disruption of follicular growth. The timing of follicular disruption is also related to ambient temperature because the proportion of female Blue Tits that cease to lay increases when higher temperatures occur toward the end of laying. It is suggested that the use of temperature to control clutch‐size may be adaptive because the food peak on which parents rely to feed their chicks is likewise affected by temper

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1993.tb02812.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY