Intraspecific host selection of Père David's deer by cattle egrets in Dafeng, China

• Cattle egrets gain more foraging earnings when following Pere David's deer.
• Cattle egrets prefer following with a female deer rather than a male or a fawn.
• Cattle egrets maximize their earnings when following a female.
• We confirmed the intraspecific host selections of cattle egrets.

Studies have focused on foraging ecology of cattle egrets (Bubulcus ibis) and their selection of ungulate host species. However, few studies have been conducted at intraspecific levels, such as the sex/age class of a specific ungulate. In this study, the foraging behavior and intraspecific host selection of cattle egrets associated with Père David's deer (Elaphurus davidianus) were investigated at the Dafeng National Nature Reserve, China in summer 2011 and 2012. Egret-deer pairing status was analyzed and intraspecific host selection index was calculated. Cattle egrets preferred to feed with female deer compared with male deer and fawns. In contrast to solitary birds, cattle egrets following a deer benefited from a relatively low vigilance output, high foraging success, low energy expenditure, and high total foraging yields. These egrets also maximized benefits when they followed female deer compared with male deer and fawns. Our results further indicated that egrets likely preferred females because of the appropriate moving speed that allowed these egrets to follow and forage sufficiently and effectively. The males of Père David's deer were possibly more aggressive than the females during the rutting season, causing egrets to experience difficulty in accompaniment and feeding. Fawns were not preferred because they were usually motionless and insufficiently large to stir more insects. We did not find any behavioral differences in vigilance and feeding between juveniles and adults. Our results suggested that cattle egrets could obtain significant benefits from their association with Père David's deer, and these benefits were maximized when they followed female deer.This article is part of a Special Issue entitled: insert SI title.