Open AccessNest site characteristics of cavity-nesting birds on a small island, in Haida Gwaii, British Columbia, Canada
Author(s) -
Neil G. Pilgrim,
Joanna L. Smith,
K. G. Moore,
Anthony J. Gaston
Publication year - 2020
Publication title -
canadian field-naturalist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 28
ISSN - 0008-3550
DOI - 10.22621/cfn.v133i4.2277
Subject(s) - snag , nest (protein structural motif) , nest box , fledge , ecology , biology , diameter at breast height , avian clutch size , geography , habitat , predation , reproduction , biochemistry
Many studies of cavity-nesting birds in North America are conducted in large continental forests and much less is known about them in island ecosystems. We describe a 29-year study of tree species, nest site characteristics, and fledge dates of cavity-nesting birds on a small island in Haida Gwaii, British Columbia (BC). Seven cavity-nesting bird species were documented on East Limestone Island and 463 nests were found in 173 different trees. Nest trees were significantly taller and had a greater diameter than a random sample of snags. Tree height did not differ among bird species but diameter at breast height was larger for trees used by Brown Creeper (Certhia americana) than for other species. Cavity-nesters selected tree decay classes 2–7 (all dead/near dead [snags]), with 85% in decay class 4 (35%) or 5 (50%), similar to the random snag sample (class 4, 32%; class 5, 42%). Cavity height ranged from 2.6 to 44.9 m and for all species, except Brown Creeper, the mean nest height was >60% of the mean tree height. Nest heights were generally greater than observed elsewhere in BC. Nest cavity orientation was random except for Red-breasted Sapsuckers (Sphyrapicus ruber), for which only 13% of the cavity entrances faced southeast. Median fledging dates ranged from 7 June (Chestnut-backed Chickadee [Poecile rufescens]) to 28 June (Northern Flicker [Colaptes auratus]). Estimated median dates of clutch completion were similar for all species. Our results show that large snags provide habitat for a high diversity of cavity-nesting birds on Haida Gwaii.