| Abstrakt: |
In 2008-2011, social attraction (i.e. provision of artificial nests and nocturnal vocalization broadcasting) was used to restore a small colony of Ashy Storm-Petrels Oceanodroma homochroa at Orizaba Rock off Santa Cruz Island, California, United States. This colony had declined 74.1% front 27 nests (1996) to 7 (2005), or -17.5% per year (1995-2004) using a colony size index. In contrast, a nearby reference colony. Cave of the Birds' Eggs, increased 72.7% from 11 (1995) to 19 nests (2005) but colony size index trend (1995-2004) was non-significant. With social attraction, number of nests at Orizaba Rock almost tripled from the baseline mean of 12 (2005-2007) to 33 (2011), reflecting increases of 22.4% per year using the colony size index (2005-2011) or 26.5% per year based on colony size (2005-2011). In 2008, four eggs were laid in artificial nests; by 2011, petrels laid eggs at 11 of 30 (36.7%) artificial nests and visited nine more (30.0%). In comparison, reference colony size increased from the baseline mean of 22 nests (2005-2007) to 24 nests (2011) or 9.3% per year using the colony size index (1995-2011). Relatively high breeding success at both colonies in 2005-2011 apparently reflected reduced organochlorine pollutants, adequate prey resources, relatively low avian predation, and low or no impacts from squid-fishing lights. In 2010, Common Ravens Corvus corax discovered and dismantled 12 artificial nests; modifications were made in 2011 to prevent raven access. Social attraction resulted in restoration of the Orizaba Rock colony to its 1996 size, demonstrating the technique's effectiveness in increasing colony size and encouraging storm-petrel use of artificial sites. [ABSTRACT FROM AUTHOR] |
