Download the article (low-res pdf) here (624 kB)

 

Introduction

Nicolas Martinez and I wrote an article about the identification and temporal distribution of hybrid male redstarts and Eastern Black Redstart: 

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van der Spek, V. & N. Martinez (2018). Identification and temporal distribution of hybrid redstarts and Eastern Black Redstart in Europe. Dutch Birding 40:3

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Summary

It's been well described in the past that hybrid Common x Black Redstart can look scarily similar to Eastern Black Redstart ssp. phoenicuroides (e.g. Nicolai et al 1996; Steijn 2005). The wing structure (well-described by Steijn 2005) was therefore often considered the diagnostic feature for a certain ID. Our conclusion, based on plumage analyses of 62 hybrid males and 50 male phoenicuroides, is that nearly all males can be identified on plumage alone. The analyses includes both formerly described and new features (table 1). The features presented in the table are present in (an often substantial) part of the hybrids, while they are uncommon or rare (category 2) or non-existent (category 1) in phoenicuroides. An important new feature is the shape and size of the breast patch, since this seems to rule out phoenicuroides in half of all hybrids. The analyses shows that based on plumage characters, 93.5% of the hybrids in our sample caused no serious ID headaches. Only one bird in the entire sample proofed to be truly problematic and could be mistaken for Eastern Black. 

 

Furthermore, analyses of the temporal distribution shows that hybrids are virtually absent when Eastern Black arrives, and vice versa.

 

To paraphrase Andy Stoddart (2016): if a suitable looking bird pops up in northern Europe in late autumn or winter, Eastern Black Redstart is the default option - not a hybrid.