Data from: Variation in laying date in relation to spring temperature in three species of tits (Paridae) and pied flycatchers Ficedula hypoleuca in southernmost Sweden

This study documents the advancement of laying dates in three species of tits (Paridae) in southernmost Sweden during recent decades, and the absence of a similar response in the pied flycatcher Ficedula hypoleuca. It is based on several different nestbox studies; the oldest one starting in 1969. During 1969 to 2012, mean spring temperatures in the study area increased by between 0.06 and 0.08°C per year, depending on the period considered. Great tits Parus major, blue tits Cyanistes caeruleus and marsh tits Poecile palustris, which generally start egg laying between the last week of April and the first week of May, all advanced laying date at a similar rate during the study period (0.25 d yr–1). This indicates that these species were similarly affected by increasing temperatures. When accounting for mean spring temperature variation, we still found an advancement of laying date over the study period, mostly due to such relationships among marsh and blue tits. This result could reflect ongoing microevolution favouring earlier laying, but could also be a result of other factors such as increased intra- or inter-specific competition for early breeding. Pied flycatchers, which generally lay during the third week of May, did not significantly advance the date of egg laying despite that the long-term trend in the increase in ambient temperature during the 30-d period preceding the start of egg laying was similar for pied flycatchers compared to the tit species.

本研究记录了近数十年来瑞典最南部地区三种山雀（山雀科Paridae）的产卵日期提前现象，以及斑姬鹟（Ficedula hypoleuca）未出现类似响应的情况。本研究基于多项不同的巢箱（nestbox）研究，其中最早的一项始于1969年。1969年至2012年间，研究区域的春季平均气温以每年0.06至0.08℃的速率上升，具体增幅取决于所选取的研究时段。大山雀（Parus major）、蓝山雀（Cyanistes caeruleus）与沼泽山雀（Poecile palustris）通常在4月最后一周至5月第一周期间开始产卵，在研究期内三者的产卵日期均以相近的速率提前（0.25天·年⁻¹）。这表明上述物种受气温上升的影响程度相近。在纳入春季平均气温的变异因素后，研究仍发现产卵日期在研究期间存在提前趋势，该现象主要见于沼泽山雀与蓝山雀。该结果或反映了当下正发生的、倾向于提早产卵的微进化（microevolution）过程，也可能源于其他因素，比如种内或种间为提早繁殖而加剧的竞争。斑姬鹟通常于5月第三周产卵，尽管其产卵前30天的环境气温长期上升趋势与三种山雀相近，但该物种的产卵日期并未出现显著提前。