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

V. OJEDA +23

AUK

AMER ORNITHOLOGISTS UNION

Año: 2020 vol. 138

0004-8038

In the NorthernHemisphere, several avian cavity excavators (e.g., woodpeckers) orient theircavities increasingly toward the equator as latitude increases (i.e., farther north),and it is proposed that they do so to take advantage of incident solarradiation at their nests. If latitude is a key driver of cavity orientationsglobally, this pattern should extend to the Southern Hemisphere. Here, we testthe prediction that cavities are oriented increasingly northward at higher (i.e.,colder) latitudes in the Southern Hemisphere and describe the preferred entrancedirection(s) of 1501 cavities excavated by 25 avian species (n = 22Picidae, 2 Trogonidae, 1 Furnariidae) across 12 terrestrial ecoregions (15°S ?55°S) in South America. We used Bayesian projected normal mixed-effects models forcircular data to examine the influence of latitude, and potential confoundingfactors, on cavity orientation. Also, a probability model-selection procedurewas used to simultaneously examine multiple orientation hypotheses in eachecoregion to explore underlying cavity-orientation patterns. Contrary topredictions, and patterns from the Northern Hemisphere, birds did not orienttheir cavities more toward the equator with increasing latitude, suggestingthat latitude may not be an important underlying selective force shapingexcavation behavior in South America. Moreover, unimodal cavity-entrance orientationswere not frequent among the ecoregions analyzed (only in four ecoregions), whereasbimodal (in five ecoregions) or uniform (in three ecoregions) orientations werealso present, although many of these patterns were not very clear. Our results highlightthe need to include data from under-studied biotas and regions to improveinferences at macroecological scales. Furthermore, we suggest a re-analysis ofNorthern Hemisphere cavity orientation patterns using a multi-model approach, anda more comprehensive assessment of the role of environmental factors as driversof cavity orientation at different spatial scales in both hemispheres.