FEATURE
autumnalis with four confirmed and two suspected. Using the 258 ha, the estimated nest
densities were 7.0 (confirmed) to 8.5 (suspected) nests per 100 hectares for all three species combined. Confirmed nesting density per 100 ha was 1.6 nests for A. autumnalis, 2.3 for A. oratrix and 3.1 for A. viridigenalis. The nesting densities for A. oratrix were 270% to 360% higher in 2013 than the average during 1993 to 1998. This increase is real as during the 1990s research teams never found eight or more nests of this species even though they searched an area roughly twice the size of that searched in 2013. The nest density of A. viridigenalis, was about 36% higher in 2013 than in 1993 to 1998. This likely represents a real increase, although not nearly as pronounced as that seen for A. oratrix. The nest density for A. autumnalis in 2013 was nearly identical to the 6 year average (1993 to 1998). However, given the late start on the field season (April – May in 2013 versus February – May in the 1990’s) and the smaller field team, the expectation was to find lower numbers of nests in the 2013 season, especially for A. autumnalis which is exceedingly cautious around its nest making its nests much more difficult to find. Additional nest searching effort would likely pay off a great deal more in finding nests of A. autumnalis and for this reason it is suspected that the actual nest densities
of A. autumnalis may also be higher in 2013 than they were in the 1990’s. However, the results clearly show that all three species are still surviving and nesting at Los Colorados Ranch. Another factor is that the region is still in the grips of a serious drought, which began in 2010. Nevertheless, the visits to the research site confirm confirm the similarities in the 1993 habitat map and the 2010 Google Earth images. The nest data from 2013 show that
there is still some nest-poaching happening, however the Los Colorados Ranch owner, as a result of his interest in the repeat project, now receives reports from his manager so as to maintain control of these kinds of activities on his land. This is good news for the Amazons of Tamaulipas.
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BIRD SCENE 41
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