# Characterization of the Worthen Sparrow (Spizella wortheni)’s Nest Building Materials in Northeastern Mexico

## TL;DR

This study identifies Muhlenbergia torreyi as the primary plant material used by Worthen sparrows to build nests in northeastern Mexico.

## Contribution

The study provides the first detailed characterization of nest-building materials used by the endangered Worthen sparrow.

## Key findings

- Muhlenbergia torreyi constituted 85.5% of the total biomass in Worthen sparrow nests.
- Five other plant species made up an additional 9.1% of the nest biomass.
- Animal materials like horse and cow hair were present but made up less than 2% of the biomass.

## Abstract

The Worthen sparrow (WS) is an endemic species of the Mexican rangelands that is considered endangered. The objective of this study was to document the building materials for nest building of this obligate grassland bird species. After completing the breeding season from 2013–2016, 207 empty nests were collected to analyze the construction materials used in their assembly. The findings revealed that Muhlembergia torrey was a key component of the WS’s nest.

The study was conducted within a well-managed beef cattle operation in northeastern Mexico. Each nest was weighed and dissected to obtain the plant and animal material used to build the nests. The number of materials present per nest and relative frequency were determined. Twenty-one building materials were used. Over the years, Muhlenbergia torreyi represented 85.5% of the total biomass of the nests, and Aristida longiseta, Bouteloua gracilis, Brickellia canescens, Purshia mexicana and Cirsium ehrenbergii constituted 2.45, 2.80, 2.44, 1.34 and 1.11% of the total biomass, respectively. The above-mentioned grasses represented 95.62% of the total biomass. Material of animal origin was horse and cow hair, which represented 0.84 and 0.58% of the total biomass, respectively. It was concluded that, at the study site, Muhlenbergia torreyi was a key nest-building material for the Worthen sparrow nest.