Latitude does not influence cavity entrance orientation of South American avian excavators

OJEDA, VALERIA; SCHAAF, ALEJANDRO; ALTAMIRANO, TOMÁS A; BONAPARTE, BIANCA; BRAGAGNOLO, LAURA; CHAZARRETA, LAURA; COCKLE, KRISTINA; DIAS, RAPHAEL; DI SALLO, FACUNDO; IBARRA, J TOMÁS; IPPI, SILVINA; JAUREGUI, ADRIÁN; JIMÉNEZ, JAIME E; LAMMERTINK, MARTJAN; LÓPEZ, FERNANDO; NÚÑEZ MONTELLANO, MARÍA GABRIELA; DE LA PEÑA, MARTÍN; RIVERA, LUIS; VIVANCO, CONSTANZA; SANTILLÁN, MIGUEL; SOTO, GERARDO E; VERGARA, PABLO M; WYNIA, AMY; POLITI, NATALIA

AUK

AMER ORNITHOLOGISTS UNION

Año: 2021

0004-8038

In the Northern Hemisphere, several avian cavity excavators (e.g., woodpeckers) orient their cavities increasinglytoward the equator as latitude increases (i.e. farther north), and it is proposed that they do so to take advantage ofincident solar radiation at their nests. If latitude is a key driver of cavity orientations globally, this pattern should extendto the Southern Hemisphere. Here, we test the prediction that cavities are oriented increasingly northward at higher(i.e. colder) latitudes in the Southern Hemisphere and describe the preferred entrance direction(s) of 1,501 cavitiesexcavated by 25 avian species (n = 22 Picidae, 2 Trogonidae, 1 Furnariidae) across 12 terrestrial ecoregions (15°S to 55°S)in South America. We used Bayesian projected normal mixed-effects models for circular data to examine the influenceof latitude, and potential confounding factors, on cavity orientation. Also, a probability model-selection procedurewas used to simultaneously examine multiple orientation hypotheses in each ecoregion to explore underlying cavityorientationpatterns. Contrary to predictions, and patterns from the Northern Hemisphere, birds did not orient theircavities more toward the equator with increasing latitude, suggesting that latitude may not be an important underlyingselective force shaping excavation behavior in South America. Moreover, unimodal cavity-entrance orientations werenot frequent among the ecoregions analyzed (only in 4 ecoregions), whereas bimodal (in 5 ecoregions) or uniform(in 3 ecoregions) orientations were also present, although many of these patterns were not very clear. Our resultshighlight the need to include data from under-studied biotas and regions to improve inferences at macroecologicalscales. Furthermore, we suggest a re-analysis of Northern Hemisphere cavity orientation patterns using a multi-modelapproach, and a more comprehensive assessment of the role of environmental factors as drivers of cavity orientation atdifferent spatial scales in both hemispheres.