, 2013). Moreover, the high nest reuse in the same nest and the low nest alternation observed for both species would also explain this nest reuse pattern in territorial reoccupancies. Although other species maintain multiple nests to reinforce the territory, for example with an average of 6.9 nests per territory in golden eagles Aquila chrysaetos (Kochert & Steenhof, 2012), our species had few nests per territory (1.6 nests on average) mostly formed by one nest (50.75%). This prevalence of nest reuse in our study area underlines the importance of preserving old nests. Nest construction involves a considerable investment

of time and energy that could be reallocated directly to reproduction if nests were reused, possibly resulting in larger clutch sizes (Redmond et al., 2007) or in earlier clutch initiation (Cavitt et al., 1999). Nest building effort is even JNK inhibitor greater in some raptors, since each pair maintains or builds several nests and uses different nests in different years (up to 10 nests per pair in some cases; Fernández & Azkona, 1993; Ontiveros et al., 2008; Kochert & Steenhof, 2012) so breeding success could be limited by the availability of nesting sites. Our findings did not support the hypothesis that building a nest has a cost in reproductive output, and both booted eagle and common buzzard pairs clearly benefited from nest reuse buy CX-5461 by having a high

probability of breeding success, or more fledglings. In agreement with these results, nest building does not influence reproductive output by tree swallows Tachycineta bicolour (Rendell & Verbeek, 1996). In most papers reviewed by Mazgajski (2007), the presence of old nest holes did not influence breeding parameters. Nevertheless, the effects of nest building on reproductive output had different trends in new establishments and reoccupancy events. Newly established booted eagle pairs had a probability of breeding success and productivity

significantly higher when they built new nests than when they reused nests. Newly established common buzzards followed the same tendency with a higher probability of breeding success than booted 上海皓元 eagles (71.43 vs. 58.33%), since common buzzards are sedentary, avoiding the time and energetic costs involved in migration. Another study in the area concluded that territory quality was not relevant in the breeding success of booted eagle (Pagán et al., 2009), so we suggest that this effect on reproductive output could be due to booted eagle pairs having high individual quality, which they invest both in the building of new nest and breeding performance. These more successful newly established pairs tend to build nests, especially in new territories, and they are likely to be experienced individuals which do not follow territorial fidelity after breeding success the previous year (∼ 30% by booted eagles; Jiménez-Franco et al., 2013).