Woodpeckers and non-excavator birds in logged sites: same problem... same solution?

CONSTANZA VIVANCO; ROMAN RUGGERA; NATALIA POLITI; ALEJANDRO A. SCHAAF; LUIS RIVERA; EVER TALLEI

Jyväskylä

Simposio; 5th European Congress of Conservation Biology; 2018

Piedmont forests, the lower vegetation stratum of Andean forests in NW Argentina, have been severely disturbedwith ~90% of its original range transformed into agricultural, live-stock pastures, industrial, and urban areas.One main current human activity in piedmont forest remnants is selective logging, legal and illegal, and alwayswithout criteria for biodiversity conservation. As part of a project aiming to preserve the biodiversity ofpiedmont forests, we show a study in progress on cavity-user birds, emphasizing on woodpecker species. Wehave conducted 3 field seasons at 3 undisturbed sites (US) and 4 logged sites (LS) with comparable sampleeffort, performing point counts to detect differences in cavity-user bird abundances, and looking for cavities usedby birds (i.e. nests or roosts). We applied network theory to analyze these bird-tree interactions, i.e. nestwebs.We found that 14 of 22 cavity user bird species (e.g. toucans, parrots, flycatchers, woodcreepers, andwoodpeckers) were significantly less abundant in LS than in US; particularly, from 4 woodpecker speciesoccurring at our study area, only the White-barred Piculet (Picumnus cirratus) did not show significantdifferences in abundance between sites, and the Golden-olive Woodpecker (Colaptes rubiginosus) was notdetected at LS. We found 143 cavities (i.e. interactions) in 14 tree species used by 14 bird species in US, and 66cavities in 12 tree species used by 13 bird species in LS. Difference in the amount of interactions between USand LS was mainly due to woodpecker incidence: 108 vs 35 interactions respectively. Several networkparameters, such as connectance, dominance, evenness, and robustness against tree species extinctionsimulations, were similar between US and LS. Woodpecker cavities were only occasionally used by nonexcavators,both in US (18.7% of non-excavator interactions) and LS (19.4%). We found differences in thefollowing aspects: 1) key tree species, determined by strength index, were snags (i.e. standing dead trees),Calycophyllum multiflorum and Amburana cearensis (an endangered Fabaceeae) in US, and snags,Anandenanthera colubrina and Astronium urundeuva in LS; 2) the whole nestweb, as well as the 4 woodpeckerspecies, were more generalists in US than in LS, probably caused by a shortage of suitable trees in LS; and 3) UShad 2 interaction modules: one formed by excavators (woodpeckers plus a trogon) that excavated their owncavities in snags and in living trees, and the other by non-excavators mainly with decay-formed cavities in livingtrees, but also in snags; LS had a third module in which a few non-excavator species, absent in US, constituted aseparate module with decay-formed cavities in snags. Our results show that selective logging is heavilyinfluencing the woodpecker occurrence in LS, and that actions tending to preserve woodpeckers could have noimpact on non-excavator cavity-users in our study site.