Nest characteristics of the Eastern Rock Nuthatch (Sitta tephronota) in southwestern Iran

Abstract

In the springs of 2015–2017, the population size and nest characteristics of the Eastern Rock Nuthatch (Sitta tephronota) were investigated. The study was conducted in a 400 hectare area of the mountainous region of southwestern Iran. In 2016, the population of the Eastern Rock Nuthatch was estimated at 33 pairs and its density was 8.25 breeding pairs per 100 ha of the study area. During the study, 45 nuthatch nests were investigated, of which 15 (33%) were found in cliffs and 28 (62%) were located in tree holes; 2% were built in house and bridge walls. The height of the nest was 214.3±112.3 cm above ground level. The mean of the horizontal and vertical depths of the nest chambers in trees was 17.8±3.7 and 12.6±3.2 cm respectively, and statistically differed from those in rocky nests (respectively 23.9±5.5 and 10.8±4.6 cm). However, chamber volumes did not statistically differ between these two nest type categories. The inner entrance areas of rocky nests were significantly smaller than those located in tree holes (respectively 11.1±2.3 and 15.3±5.5 cm2). Our findings suggest that differences in nest characteristics may be an adaptation of the Eastern Rock Nuthatch to predation.