Effects of rainfall on bird reproduction in a semi-arid Neotropical region

ABSTRACT In semi-arid ecosystems, birds commonly use rainfall as a reliable environmental cue to adjust the timing and strength of their reproductive activity. Here we evaluate this hypothesis for a community of birds in the Caatinga (the semi-arid region of northeastern Brazil), using brood patch information and nest abundance. Sampling occurred every 14 days between September 2012 and August 2013 (brood patch), and every three or four days during the reproductive period (nests). Abundance of brood patches and nests were correlated, and all brood patches were recorded between March and July (4.5 to 5.0 months). We recorded three peaks of brood patch abundance: the first 28 days after the first rains, the second 14 days after the second rainfall peak, and the third synchronously with the third rainy period. These results indicate that intra-annual variation in local rainfall has the potential to account for variations in the timing and intensity of reproduction in the studied birds.

摘要：在半干旱生态系统中，鸟类通常将降雨作为可靠的环境线索，以此调整繁殖活动的时间节点与强度。本研究针对巴西东北部半干旱区域卡廷加（Caatinga）的鸟类群落，借助孵卵斑（brood patch）数据与巢多度（nest abundance）对该假说进行验证。采样方案如下：2012年9月至2013年8月期间每14天采集一次孵卵斑数据，繁殖期内则每3至4天开展一次巢多度调查。研究发现，孵卵斑多度与巢多度呈显著相关，且所有孵卵斑记录均集中于3月至7月（时长约4.5至5.0个月）。本研究共观测到三次孵卵斑多度峰值：首次峰值出现在首轮降雨后28天，第二次峰值出现在第二轮降雨高峰后14天，第三次峰值则与第三轮降雨时段完全同步。上述结果表明，局地降雨的年内变化可解释本研究涉及鸟类的繁殖时间与繁殖强度差异。