alvarosaurus's Journal

There are two species of European treecreepers: The short-toed treecreeper (Certhia brachydactyla) and the Eurasian or common treecreeper (Certhia familiaris). These species are notoriously difficult to tell from each other: on iNaturalist, out of 344 observations of treecreepers in Europe, 90 (26%) have not reached research grade. By comparison, the genus Phoenicurus, which also has two European species, has been observed on iNaturalist 1109 times in Europe, out of which 15 observations (0,01%) have not reached research grade.

Barring DNA analysis, there are 3 ways to tell bird species apart: by morphological traits, behaviour and ecological preferences (range and habitat).

Range

The ranges of the two species overlap in most of Europe. An exception to this are the British Isles, where only the the Eurasian or common treecreeper (Certhia familiaris) is present.

Habitat

The Eurasian or common treecreeper (Certhia familiaris) prefers coniferous trees, while the short-toed treecreeper (Certhia brachydactyla) prefers oaks and mixed forests.

Morphology

The Eurasian or common treecreeper (Certhia familiaris) has a whiter underpart, contrasted supercillium and a shorter bill (fig. 1). Fig. 1: Eurasian or common treecreeper (Certhia familiaris), observed by Martin Grimm.

While the the short-toed treecreeper (Certhia brachydactyla) has a browner underpart, less marked supercillium and a longer bill (fig. 2). Fig. 2: Short-toed treecreeper (Certhia brachydactyla), observed by Tania Araujo.

Behaviour

Treecreepers can be told apart by ear.

The Eurasian or common treecreeper (Certhia familiaris) sings a vibrating and shrill tone.

While the Eurasian or common treecreeper (Certhia familiaris) sings a series of notes.