Comparison of nesting ecology of three co-existing Atlantic Forest woodpeckers reveals narrow specialization in the Helmeted Woodpecker (Celeus galeatus)

COCKLE, KRISTINA L; LAMMERTINK, MARTJAN; FERNÁNDEZ, JM

Congreso; 8th International Woodpecker Conference; 2019

The Atlantic Forest in southeastern South America is a biodiversity hotspot with high species richness and high forest loss. Three large to medium sized woodpecker species (Robust Woodpecker Campephilus robustus, 265g, Lineated Woodpecker Dryocopus lineatus, 209 g, and the old-growth specialist, globally threatened Helmeted Woodpecker Celeus galeatus, 129 g) coexist in the southern portion of the ecoregion, and show remarkable convergence in plumage patterns and colouration, possibly driven by interspecific interactions. We examined nest tree species, nest substrates, and timing of breeding, to assess differentiation in these niche dimensions and to evaluate whether nesting ecology may be a factor explaining an association with mature forests in the Helmeted Woodpecker. Robust and Lineated Woodpeckers excavated cavities in a wide diversity of nine and eight nest tree species, respectively, whereas Helmeted Woodpeckers specialized narrowly on laurel trees (88% of nest cavities in two species in genus Nectandra). Helmeted Woodpecker is further distinguished by a more frequent use of living, partially decayed trees (69%, vs 13% for Robust and 35% for Lineated) and by more frequent re-use of nest cavities (32%, vs 0% for Robust and 0% for Lineated). When nesting in selectivelylogged forest (vs. old-growth), Robust and Lineated Woodpeckers used trees withsmaller DBH (mean 48 vs 79 cm for Robust and 34 vs 60 cm for Lineated) and Robust Woodpeckers excavated lower in trees (9 vs 17 m).Helmeted Woodpeckers selected nest trees with similar dimensions in both environments (mean DBH 51 cm, height 9 m), indicating lesser flexibility. Helmeted Woodpeckers bred 20-23 days later in the year than Lineated and Robust Woodpeckers, potentially allowing them to avoid nesting near the two larger species. The narrow specialization of Helmeted Woodpecker on nesting in Nectandra trees of specific sizes and conditionsis a possible factor in making it more sensitive to selective logging effects. Nectandra trees are fairly common in the Atlantic Forest and are less desirable timber trees, but are exploited at increasing frequency.