Unusual late mass occurrence of the Common Swift (Apus apus (Linnaeus, 1758)) (Aves: Apodidae) in Sofia (Bulgaria)

Abstract

An observation of about 120 Common Swifts over the central part of the Sofia City on 15 October is reported.

Keywords

• Common swift
• avian phenology
• autumn migration
• urban avifauna
• swifts in Bulgaria