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Titolo:
Winter age ratios and the assessment of recruitment of Harlequin Ducks
Autore:
Smith, CM; Goudie, RI; Cooke, F;
Indirizzi:
Simon Fraser Univ, Dept Biol Sci, Ctr Wildlife Ecol, Burnaby, BC V5A 1S6, Canada Simon Fraser Univ Burnaby BC Canada V5A 1S6 , Burnaby, BC V5A 1S6, Canada Canadian Wildlife Serv, Pacific Wildlife Res Ctr, Delta, BC V4K 3N2, Canada Canadian Wildlife Serv Delta BC Canada V4K 3N2 Delta, BC V4K 3N2, Canada
Titolo Testata:
WATERBIRDS
fascicolo: 1, volume: 24, anno: 2001,
pagine: 39 - 44
SICI:
1524-4695(2001)24:1<39:WARATA>2.0.ZU;2-1
Fonte:
ISI
Lingua:
ENG
Soggetto:
SIZE;
Keywords:
age ratios; British Columbia; Harlequin Duck; Histrionicus histrionicus; recruitment; Strait of Georgia;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Citazioni:
26
Recensione:
Indirizzi per estratti:
Indirizzo: Smith, CM Pk Canada Agcy, Box 900, Banff, AB T0L 0C0, Canada Pk Canada Agcy Box 900 Banff AB Canada T0L 0C0 B T0L 0C0, Canada
Citazione:
C.M. Smith et al., "Winter age ratios and the assessment of recruitment of Harlequin Ducks", WATERBIRDS, 24(1), 2001, pp. 39-44

Abstract

Recruitment in the process by which young birds are added to tile breedingpopulation. The two most commonly used methods to estimate recruitment in ducks are pair/brood counts, and fall age ratios based on wings returned byhunters. Direct counts on the wintering al-ea to determine the proportion of young males to adult males (age ratios), can be used for species with delayed plumage maturation. This is useful for species that are difficult to study on tile breeding grounds and are seldom hunted, such as Harlequin Ducks (Histrionicus histrionicus). Such an approach is only valid if age classes are equally sampled. Between 1994 and 1999, the proportion of male Harlequin Ducks that were immatures in thr Strait of Georgia, British Columbia, Mas estimated at 0.068. The proportions differed across years. Little difference occurred through the winter months until spring, when there was a significant increase in proportions in March. If these age ratios are accurate, then recruitment would not be compensating for annual adult mortality andthe population could have been declining during the period of our study. However, if immature males are not distributed evenly among the population, then our assessment may underestimate ol overestimate proportions. Delayed breeding means that immature birds experience several additional seasons ofmortality prior to breeding, and thus the actual recruitment I ate into the breeding population would be lower than tl-lat presented here.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/04/20 alle ore 12:10:31