Cardinal orientation of cavities excavated by birds in the Neotropics: relationship with macro-environmental attributes.

OJEDA, V. (>20)

Puerto Iguazú

Congreso; Ornithological Congress of the Americas (Association of Field Ornithologists, Sociedade Brasileira de Ornitologia y Aves Argentinas); 2017

The microclimate of avian nest and roost sitesaffects reproduction and survival; therefore, environmental placement of thesestructures is of adaptive significance. It has been hypothesized that, tooptimize thermal properties, at higher latitudes avian excavators should orienttheir cavities more toward the equator. In support of this, a meta-analysis ofcavity entrance orientation of Northern Hemisphere woodpeckers showed that withincreasing latitude cavities were oriented more toward the south. We testedthis hypothesis, with the inverse prediction (dominance of north orientationsas latitude increases), for cavities excavated in the Southern Hemisphere, withdata from nine Neotropical ecorregions, including tropical to subpolar sites(~16-55° S, ~48-72° W). We recorded orientations for nests and/or roosts(n=1511) excavated in trees, poles, and terrestrial termite mounds by 25species varying in size, from Picumnusto Campephilus. Based on severalgeneralized linear models, we found that macro environmental variables  (such as altitude, latitude, or ecorregion)failed to predict orientation. Cavities were randomly oriented in Cerrado,Chaco,  Atlantic Forest and Pampasecorregions. However, they were non-random in Yungas and Monte (facingwest-southwest), Espinal (north), Valdivian (east) and Magellanic(north-northeast) ecorregions. These results do not support the prediction thatat higher latitude birds orient their cavities more toward the equator, andcast doubt on latitude as a global driver of cavity orientation. Othermacro-environmental variables (such as reduced continentality in the southernNeotropics) might cancel out the effects of latitude. Further, local variablesmay explain the patterns occurring at each ecorregion.