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The timing of birds' breeding seasons: a review of experiments that manipulated timing of breeding

Verhulst, Simon and Nilsson, Jan-Åke LU (2008) In Royal Society of London. Philosophical Transactions B. Biological Sciences 363(1490). p.399-410
Abstract
Reproductive success usually declines in the course of the season, which may be a direct effect of breeding time, an effect of quality (individuals with high phenotypic or environmental quality breeding early), or a combination of the two. Being able to distinguish between these possibilities is crucial when trying to understand individual variation in annual routines, for instance when to breed, moult and migrate. We review experiments with free-living birds performed to distinguish between the 'timing' and 'quality' hypothesis. 'Clean' manipulation of breeding time seems impossible, and we therefore discuss strong and weak points of different manipulation techniques. We find that the qualitative results were independent of manipulation... (More)
Reproductive success usually declines in the course of the season, which may be a direct effect of breeding time, an effect of quality (individuals with high phenotypic or environmental quality breeding early), or a combination of the two. Being able to distinguish between these possibilities is crucial when trying to understand individual variation in annual routines, for instance when to breed, moult and migrate. We review experiments with free-living birds performed to distinguish between the 'timing' and 'quality' hypothesis. 'Clean' manipulation of breeding time seems impossible, and we therefore discuss strong and weak points of different manipulation techniques. We find that the qualitative results were independent of manipulation technique (inducing replacement clutches versus cross-fostering early and late clutches). Given that the two techniques differ strongly in demands made on the birds, this suggests that potential experimental biases are limited. Overall, the evidence indicated that date and quality are both important, depending on fitness component and species, although evidence for the date hypothesis was found more frequently. We expected both effects to be prevalent, since only if date per se is important, does an incentive exist for high-quality birds to breed early. We discuss mechanisms mediating the seasonal decline in reproductive success, and distinguish between effects of absolute date and relative date, for instance timing relative to seasonal environmental fluctuations or conspecifics. The latter is important at least in some cases, suggesting that the optimal breeding time may be frequency dependent, but this has been little studied. A recurring pattern among cross-fostering studies was that delay experiments provided evidence for the quality hypothesis, while advance experiments provided evidence for the date hypothesis. This indicates that late pairs are constrained from producing a clutch earlier in the season, presumably by the fitness costs this would entail. This provides us with a paradox: evidence for the date hypothesis leads us to conclude that quality is important for the ability to breed early. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
life-history evolution, clutch size, lay date, hatch date
in
Royal Society of London. Philosophical Transactions B. Biological Sciences
volume
363
issue
1490
pages
399 - 410
publisher
Royal Society
external identifiers
  • wos:000252317600012
  • scopus:37149019293
ISSN
1471-2970
DOI
10.1098/rstb.2007.2146
language
English
LU publication?
yes
id
d83d75ef-a169-44a6-86a9-017a0a5d8e66 (old id 1200024)
date added to LUP
2008-09-11 14:57:05
date last changed
2017-11-12 03:47:49
@article{d83d75ef-a169-44a6-86a9-017a0a5d8e66,
  abstract     = {Reproductive success usually declines in the course of the season, which may be a direct effect of breeding time, an effect of quality (individuals with high phenotypic or environmental quality breeding early), or a combination of the two. Being able to distinguish between these possibilities is crucial when trying to understand individual variation in annual routines, for instance when to breed, moult and migrate. We review experiments with free-living birds performed to distinguish between the 'timing' and 'quality' hypothesis. 'Clean' manipulation of breeding time seems impossible, and we therefore discuss strong and weak points of different manipulation techniques. We find that the qualitative results were independent of manipulation technique (inducing replacement clutches versus cross-fostering early and late clutches). Given that the two techniques differ strongly in demands made on the birds, this suggests that potential experimental biases are limited. Overall, the evidence indicated that date and quality are both important, depending on fitness component and species, although evidence for the date hypothesis was found more frequently. We expected both effects to be prevalent, since only if date per se is important, does an incentive exist for high-quality birds to breed early. We discuss mechanisms mediating the seasonal decline in reproductive success, and distinguish between effects of absolute date and relative date, for instance timing relative to seasonal environmental fluctuations or conspecifics. The latter is important at least in some cases, suggesting that the optimal breeding time may be frequency dependent, but this has been little studied. A recurring pattern among cross-fostering studies was that delay experiments provided evidence for the quality hypothesis, while advance experiments provided evidence for the date hypothesis. This indicates that late pairs are constrained from producing a clutch earlier in the season, presumably by the fitness costs this would entail. This provides us with a paradox: evidence for the date hypothesis leads us to conclude that quality is important for the ability to breed early.},
  author       = {Verhulst, Simon and Nilsson, Jan-Åke},
  issn         = {1471-2970},
  keyword      = {life-history evolution,clutch size,lay date,hatch date},
  language     = {eng},
  number       = {1490},
  pages        = {399--410},
  publisher    = {Royal Society},
  series       = {Royal Society of London. Philosophical Transactions B. Biological Sciences},
  title        = {The timing of birds' breeding seasons: a review of experiments that manipulated timing of breeding},
  url          = {http://dx.doi.org/10.1098/rstb.2007.2146},
  volume       = {363},
  year         = {2008},
}