Ardea
Official journal of the Netherlands Ornithologists' Union

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Perdeck A.C. & Cave A.J. (1989) Influence of temperature on the laying date of the Coot Fulica atra between-pairs and within-individuals relationships. ARDEA 77 (1): 99-106
Annual mean laying data of the first clutch of a Coot population in The Netherlands varies considerably, due to variation in the start, not the end of the laying season, resulting in less second clutches in late years. Low pre-laying temperatures delay the mean start of egg laying. To check if this holds within individuals, pre-laying temperatures were related to laying data (1st clutch) in a between-pairs and a within-individuals regression analysis. The regression coefficients of the temperature variable did not differ significantly between the two models. The relationship between temperature and laying date is therefore not due to a process of differential (local) survival. There is evidence that pre-laying temperatures act in two ways, (1) by determining the data of arrival at the territory and (2) by acting as a proximate and/or ultimate positive factor on the process that initiates egg laying when the pair is at its territory.


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