Wood hardness drives nest site selection in woodpeckers of the humid Chaco

Avian excavators (woodpeckers and other species) select nest sites based on characteristics of the nest patch, nest tree and substrate. These characteristics could increase foraging opportunities or reduce the risk of predation, but there is also a potentially important role for wood hardness in restricting nest site selection, a role that has been little explored and is expected to vary among species according to their ability to excavate. We examined patterns of nest site selection in eight woodpecker species in the humid Chaco of South America, where the dominant trees have extremely hard wood. We hypothesized that 1) wood hardness is the main factor driving selection of excavation sites, and 2) interspecific variation in body size and foraging behavior (traits frequently related to excavation ability) explain interspecific variation in the wood hardness of excavated nest substrates. From 2016 to 2019 in well-preserved forests of the Argentine Chaco, we compared nesting cavities exca..., We studied excavators and their nests during four breeding seasons (August to January) from 2016 to 2019 in Chaco National Park (28.8204°S, 59.6204°W, 14981 ha) and during two breeding seasons (2016 and 2017) in Pampa del Indio Provincial Park (26.2767°S, 59.9702°W, 8366 ha) in the humid Chaco, Chaco province, Argentina. Our data set includes 8 cavity-excavating bird species: Dryocopus schulzii (Black-bodied Woodpecker, 200 g), Picumnus cirratus (White-barred Piculet, 10 g), Melanerpes cactorum (White-fronted Woodpecker, 40 g), Celeus lugubris (Pale-crested Woodpecker, 125 g), Dryobates mixtus (Checkered Woodpecker, 30 g), Dryobates passerinus (Little Woodpecker, 37 g), Colaptes melanochloros (Green-barred Woodpecker, 135 g), and Campephilus leucopogon (Cream-backed Woodpecker, 230 g).
To obtain sufficient nest observations for analysis, we employed a case-control study design (Keating and Cherry 2004), comparing each cavity excavated in wood (nest) with a nearby potential substrate (tr..., , # Wood hardness drives nest site selection in woodpeckers of the humid Chaco

[https://doi.org/10.5061/dryad.1jwstqk4q](https://doi.org/10.5061/dryad.1jwstqk4q)

## Description of the data and file structure

We studied excavators, their nests and foraging behaviors during four breeding seasons (August to January) from 2016 to 2019 in Chaco National Park (28.8204°S, 59.6204°W, 14981 ha) and during two breeding seasons (2016 and 2017) in Pampa del Indio Provincial Park (26.2767°S, 59.9702°W, 8366 ha) in the humid Chaco, Chaco province, Argentina.

We conducted nest searches in quebrachales (about 700 hours/year) and gallery forests (about 250 hours/year).

### Files and variables

#### File: Exc\_input\_Chaco.csv

**Description:** Case-control study. Measurements of excavated nest cavities (case) by eight woodpecker species and randomly selected unexcavated substrates (control).

##### Variables

* NID: pair case/control code. 
* SpeciesID: code for the scientific name of the bird that e...