ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01958.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.1 During summer 1953, I studied Snowy Owls in Cumberland Peninsula, Baffin Island2 The wide range of call‐notes given by breeding owls is described3 Small passerines usually took little notice of the owls, though mobbing was common in July. The male owl usually chased other predators from his territory, which was exclusive of other Snowy Owls4 Some were shy of man, but others aggressive when disturbed at the nest, and males struck fiercely when they had young. Both sexes often did distraction display and displacement coition. Displacement feeding and hunting were also seen5 Threat and food‐begging, and the behaviour of the young in the nest, are described. The male brought all food to the female and young till about three weeks after the first young hatched, when the female also began to hunt6 The owls were confined to wet lowland areas where lemmings were abundant. Their density and breeding capacity were closely correlated with lemming density. Territories varied in size from a half to three or four square miles. One male was bigamous and five monogamous7 Nests were in prominent positions, and alternative sites used in previous years were found nearby8 Egg‐laying started in the third week of May as in most of the range. Mean clutch size was eight eggs9 The eggs hatched at different dates, resulting in a spread in development of the young. Most young left the nest in their fourth week; they began to fly short distances just after, but not well till about 60 days old, when they also began to hunt10 Proportionate changes in weight of the young were greatest in the first few days. On the whole they grew faster than young of various other predator species. Later‐hatched young tended to grow slower than earlier‐hatched young. All young that hatched also fledged, including 15 young in the one territory held by the bigamous male11 Each young ate an average of about two full‐grown lemmings a day while in the nest. Adults ate three to five each in a day, and in the London Zoo about 180 gm. each per day. An estimate was made of the proportion of the lemming population taken by the owls12 The relation of changes in lemming populati

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01959.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.Structural colours in birds are surveyed systematically. From this survey, the common structural configurations in feathers, producing bright colours of the iridescent and non‐iridescent types respectively, are seen to exclude one anotherFeather pigments of unusual shades or chemical constitutions have been included in the survey, since some of them produce colour effects similar to structural colours of the non‐iridescent

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01960.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.The distribution variation, moult and biology ofFalco peregrinus babylonicusare discussed

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01961.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.1 Migration was studied in the Bosphorus‐Dardanelles area between 11 September and 1 October 1956. On most days observations were made at two or more places2 Daily counts of migration of soaring birds are given. Honey BuzzardsPernis apivoruscrossed the Bosphorus on a front up to ten miles wide, and not more than a fifth or a tenth of the total could be seen from any one point. Some other species passed in narrower streams3 Different species of birds of prey passed to a large extent by different routes4 Moderate cross‐winds deflected the streams of soaring‐birds (especially eaglesAquilaspp.) downwind5 Diurnal migrant passerines passed in large numbers through the western half of the area; the migration was on a broad front and often inconspicuous. In the Bosphorus area passerine migration was frequently towards the northwest6 Very large, fluctuating numbers of night‐migrants were seen along the Bosphorus, but fewer in the Dardanelles area7 It is thought that European Turkey is an important area of concentration for some northern passerine species8 Some water birds were seen following the Bosphorus southwards9 The apparent changes in the abundance of some of the migrant species over the centuries ar

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01962.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

Summary.During the latter half of September observations were made at various points on the coast of southwest Portugal. A great many migrants were seen, especially close to Cape St. Vincent, belonging to species that winter only south of the Sahara. Bird‐catchers were in evidence on the south coast, but not on the west. Evidence was obtained that migrants are fewest with east windsMost of the birds seen must have been travelling in a southwesterly direction for a long way and it is necessary for their survival that they should change course on reaching the shores of the Atlantic. Any that did not do so might find a temporary refuge on the Canary Islands, but the list of regular passage‐migrants there is very different from that of the birds seen commonly near Cape St. Vin

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01963.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01964.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01965.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01966.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0019-1019    

DOI:10.1111/j.1474-919X.1957.tb01967.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY