Abstract
BackgroundIncubating birds must balance the conflict between thermal needs of the developing embryos and their self-maintenance needs for energy. The Chinese Grouse (Tetrastes sewerzowi) lives in high mountain conifer forests and faces energy stress, cold environment, and predation pressure. Females might adjust incubation rhythm to adapt to these constraints.MethodsTwo methods were used to investigate egg laying and incubation pattern of the Chinese Grouse; 25 nests were monitored by data loggers and 12 nests by infrared video cameras.ResultsFemale Chinese Grouses usually laid an egg every 2 days. The incubation period was 28–31 days. Overall incubation constancy for Chinese Grouse was 93%. The females took 5.0 recesses per day and 34% of all 1696 recesses were taken in the crepuscular period. The average recess duration was 20.3 min. Females took more and shorter recesses in the latter part of incubation. The females who allocated more time to foraging had a higher reproductive success.ConclusionsProbably due to its high egg/body mass ratio, the Chinese Grouse has a long laying interval of 49 h. We suggest that, due to energy stress, females have relatively more recesses and they increase the number of recesses as incubation progresses. To compensate for the embryos’ thermal needs, they extend the incubation period and shorten the recess duration in this cold environment.
Highlights
Incubating birds must balance the conflict between thermal needs of the developing embryos and their self-maintenance needs for energy
How does the Chinese Grouse deal with the cold weather, high altitude, short breeding time, and nutrient stress during the egg-laying and incubation period? In this study, we explored the egg-laying and incubation rhythms of Chinese Grouse and analyzed the strategies Chinese Grouse uses to deal with these disadvantages
In Willow Ptarmigan (Lagopus lagopus), as in many other ground-nesting precocial birds, the greatest attrition in fecundity is the loss of eggs to predators (Martin et al 1989)
Summary
Incubating birds must balance the conflict between thermal needs of the developing embryos and their self-maintenance needs for energy. Especially in those where only one sex incubates, egg laying and incubation are important stages of reproductive investment, and may represent critical energy bottlenecks, especially in harsh environments (Wiebe and Martin 1995, 1997, 2000). Incubating individuals must balance the conflict between thermal needs of the developing embryos and their self-maintenance needs by leaving the nest to forage (Wiebe and Martin 2000; Conway and Martin 2000a; Coates and Delehanty 2008). Birds living in areas with low temperatures have a higher daily energy expenditure, but foraging away from the nest is almost twice as costly as incubating a four-egg clutch (Piersma et al 2003). Because low ambient temperatures allow eggs to cool quickly, birds
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