Holbøll’s Red-necked Grebe revisited: are they doable in the field?

The identification of Red-necked Grebe subspecies primarily relies on measurements, and most accepted records of the Nearctic taxon holbollii in Europe come from deceased individuals that were accurately measured. In this post, I examine the variability of four key field identification features: bill length and shape, flank color, facial pattern, and the presence of black below the gape. In particular, I highlight the often striking differences in flank pattern between the two subspecies and use this characteristic to assess potential holbollii records from Europe.