Variation in the Relationship between Lay Date and Clutch Size in Three Cavity-Nesting Woodland Passerines

Goodenough, Anne E and Elliot, Simon L and Maitland, David P and Hart, Adam G (2009) Variation in the Relationship between Lay Date and Clutch Size in Three Cavity-Nesting Woodland Passerines. Acta Ornithologica, 44 (1). pp. 27-36. ISSN 0001-6454

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Abstract

Clutch sizes of many single-brooded birds decrease as the breeding season progresses. This decrease is usually quantified using data from several years, an approach that would mask any annual variation. We used 15 years of data from 295 nestboxes occupied by Blue Tit, Great Tit and Pied Flycatcher to determine whether the strength of the relationship between lay date and clutch size is consistent, or whether it varies annually. Both lay date and year were strong predictors of clutch size for all species. However, Generalised Linear Modelling revealed an interaction between lay date and year in the prediction of clutch size, indicating that the strength of the relationship between lay date and clutch size varied between years. Multilevel modelling was used to establish proximate factors that may be responsible for annual variability. Factors affecting the relationship between lay date and clutch size were species-specific. For Blue Tits, seasonal decline in clutch size was steepest when the density of all cavity-nesting species was high (47% variance explained). For Great Tits, decline was steepest in “early” seasons, particularly when density was high (32% variance explained), and for Pied Flycatchers, decline was steepest in warmer years (33% variance explained). Thus annually variable factors appear to influence not only breeding phenology and clutch size individually, but also the relationship between these variables.

Item Type: Article
Article Type: Article
Uncontrolled Keywords: annual variability, relative date hypothesis, lay date, clutch size, multilevel modelling, Parus major, Cyanistes caeruleus, Ficedula hypoleuca
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Schools and Research Institutes > School of Natural & Social Sciences > Environmental Sciences
Research Priority Areas: Environmental Dynamics & Governance
Depositing User: Anne Goodenough
Date Deposited: 31 Mar 2016 14:29
Last Modified: 31 Mar 2016 14:53
URI: http://eprints.glos.ac.uk/id/eprint/3327

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