Environmental and social determinants of winter fat storage in the great tit Parus major
Environmental and social determinants of winter fat storage in the great tit Parus major
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DOI：
10.2307/5695
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发表时间：
1996-01-01
影响因子：
4.8
通讯作者：
Gosler, AG
中科院分区：
文献类型：
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作者：
Gosler, AG
1.人们普遍认为，小鸟冬季脂肪储备的减少是环境限制它们进一步育肥能力的症状。与此相反，最近关于觅食和脂肪储存的理论研究表明，这种观察结果是对环境压力的战略反应，由不同个体之间不同的育肥成本和收益的平衡决定。因此，应将脂肪储备调整到所需的最低限度，以防止一段时期的压力，但鸟类应对资源差异(可预测性)以及平均丰度做出反应。因此，面临较大饥饿风险的鸟类应该比面临较低风险的鸟类携带更多的脂肪。这些假设预测，在一个具有明确的优势等级的冬季集群物种中，社会地位可能决定一只鸟获得食物的机会，不同社会地位的个体携带的脂肪储量应该不同，如下所示：(I)脂肪应该随着气温的下降而增加；(Ii)当食物充足时，白天的肥胖率应该降低；(Iii)当食物稀缺时，脂肪储备应该增加；以及(Iv)优势个体携带的脂肪应该比优势种少。这篇论文通过观察英国牛津威瑟姆森林自由生活种群中活着的大山雀的脂肪储备来验证这些预测。然后研究冬季脂肪与已知个体越冬存活之间的关系。在捕获当天，脂肪随着温度的下降而增加，而不是在之前的任何时候，这表明它在脂肪调节中起到了最接近的作用。食物越可预测，肥胖率就越低。当食物稀缺时，储备会增加，但这取决于鸟类的地位，优势种携带的脂肪比劣势种少。只有最不显性的个体才有可能受外部制约而发胖的证据。当食物充足时，脂肪储备无法预测越冬存活，这表明这些鸟能够维持它们个人的最佳储备。当食物匮乏时，低等级鸟类更有可能存活下来，而优势种的生存与肥胖无关，这表明它们仍然能够实现其个体的最佳储备。这些结果与预测一致，因此支持(I)育肥成本的论点，(Ii)育肥遵循对资源可预测性的战略反应，以及(Iii)社会地位是资源可预测性的一个组成部分。
1. It has generally been assumed that reduced winter fat reserves in small birds are symptomatic of environmental constraints on their ability to fatten further. Contrary to this, recent theoretical work on foraging and fat storage suggests that such observations result as a strategic response to environmental stress, determined by a balance of fattening costs and benefits that differ between individuals. Fat reserves should therefore be adjusted to the minimum required as insurance against some period of stress, but birds should respond to the resource variance (predictability) as well as the mean abundance. Hence, birds facing greater starvation risk should carry more fat than those facing less risk.2. These hypotheses predict that, in a winter-flocking species with a clear dominance hierarchy, and in which social status may determine a bird's access to food, individuals of different social status should differ in the fat reserves that they carry as follows: (i) fat should increase with declining temperature; (ii) the rate of diurnal fattening should be reduced when food is abundant; (iii) fat reserves should be increased when food is scarce; and (iv) dominant individuals should carry less fat than subdominants. This paper tests these predictions by observations of fat reserves of live great tits within a marked, free-living population in Wytham Woods, Oxford, UK. It then examines the relationship between the winter fat and over-winter survival of known individuals.3. Fat increased with declining temperature on the day of capture rather than at any previous time, suggesting that it acted as a proximate factor in fat regulation. The rate of fattening was lower when food was more predictable. Reserves increased when food was scarce but this depended on the bird's status, dominants carrying less fat than subdominants. Evidence that the ability to fatten might be subject to external constraint was found only in the least dominant individuals.4. When food was abundant, fat reserves failed to predict over-winter survival, suggesting that the birds were able to maintain their individual optimum reserves. When food was scarce, low ranking birds were more likely to survive ii fat, while the survival of dominants was independent of fatness, suggesting that they were still able to achieve their individual optimum reserves.5. These results agreed with the predictions, so supporting the arguments (i) for a cost of fattening, (ii) that fattening follows a strategic response to resource predictability; and (iii) that social status is a component in that resource predictability.