Individual study: Influence of old nest material in nest boxes on nest building activities of tree swallows Tachycineta bicolor at Creston Valley Wildlife Management Area, British Columbia, Canada
Rendell W. & Verbeek N. (1996) Old nest material in nest boxes of tree swallows: effects on nest-site choice and nest building. The Auk, 113, 319-328
Researchers studying hole-nesting birds breeding in nest boxes typically remove old nests from boxes prior to the next breeding season. The accumulation of old nest material might affect nest-site selection and nest building by cavity-nesting birds. This study presents the results of experiments on how old nest material influences nest building by tree swallows Tachycineta bicolor breeding in British Columbia.
Study area: The study was conducted at the Creston Valley Wildlife Management Area, British Columbia, Canada (49º05'N, 116º35'W), in 1991 and 1992. A large population of tree swallows breed in nest boxes at the site.
Nest-building experiment: Four types of boxes were tested:
(C) clean boxes - old nests removed and box scraped clean with a wire brush;
(S) 'sham' boxes - after being cleaned as C boxes, old nests were micro-waved to kill parasites (used in 1991 only);
(O) old boxes - old nest material left;
(CI) clean with inserts boxes - cleaned, and compact styrofoam and a plywood floor inserted to fill the bottom 8 cm of each box simulating the smaller cavity of boxes part-filled with old nest material (used in 1992 only).
In March 1991, before swallows began settling, C, S, and O boxes were matched into 79 pairs (each box in a pair 3 m apart), and each pair was put in a territory. In 1992, 125 boxes were redistributed as two types, C and O, arranged singly and alternately, 30-40 m apart. Fifteen randomly chosen C boxes were designated as CI boxes to examine further how cavity size influenced nest building by females.
Nest characteristics: The weight and volume of new and old nest structures were calculated before settlement and before egg laying.
b> Cost of nest building: An analysis of the cost of nest building was based on the reproductive output of 34 females in 1991, and 85 in 1992.
Nest monitoring: Breeding phenology and reproductive success were monitored during regular nest checks.
Box type significantly influenced the volume and weight of new nest material brought to nests. The weight and volume of nests built in clean boxes (24.2 g; 827 cm³) were greater than for nests built on old (5.9 g; 428 cm³) or sham (4.8 g; 307 cm³) boxes in 1991. Nests built in clean boxes (26.3 g; 712 cm³) in 1992 were larger and heavier than those built in clean with inserts (CI) boxes, and new nests in CI boxes (16.4 g; 581 cm³) were larger and heavier than those in old boxes (6.3 g; 287 cm³).
Analyses suggested that females building large nests began egg laying earlier in both years. Otherwise, there were no associations between the sizes of nests built and subsequent reproductive output (e.g. clutch size) or nestling size.
For a summary of how removing old nests from boxes can affect nest-site choice see:
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