Feather weights in Dunlin, Calidris alpina.

In 1995 Underhill & Joubert 1995 published data on the relative masses of primaries in a.o. 16 wader and 2 tern species. The development creating a need for a compilation of this kind is outlined in their introduction:

Summers (1980) and Summers et al. (1980) /WSGB 28: 24, 30: 12 - 13/ pointed out that, for waders, inner primaries are much shorter than outer primaries, and suggested adjusting for this by including feather mass in the calculations. This led to the concept of "percentage feather mass grown" (PFMG) (Summers et al. 1983). PFMG has, in several studies, been shown to increase more linearly with time than primary moult score (Summers et al. 1980, 1983, Cooper & Underhill 1991), although further transformations to PFMG may be needed to improve the linearity relative to time (Underhill et al. 1990). To compute PFMG, we need the relative masses of the primary feathers (Underhill & Zucchini 1988). These data are currently available for only a few species (Underhill et al. 1991, Table 17, Underhill & Summers 1993, Underhill & Joubert 1995). One purpose of this paper is to extend the range of species for which this information is available.

This could be called the start of a project, but like many "projects" it has lost some impetus underway (the decline of the WSG as a coordinating, over-national forum has contributed; conferences may seem coordinated, but all field-work is extremely patchy); I can see little evidence that it is pursued today. Still, what has been achieved so far is available and can be used. When reading the lists of Underhill & Joubert, I immediately regret that they haven't involved secondaries and tail as well - offering complete data for all remex crucial in flight - since it is obvious, that e.g. waders moult the energy- and nutrient-demanding outer primaries parallel with tail and secondaries, and that this period represents the moulting "effort", potentially putting the bird at risk when energy is needed for other purposes as well. It is my intention to continue this project, adding data both from species not weighed elsewhere and data concerning feathers other than primaries, like secondaries, rectrices, scapulars and primary-coverts. In a second step these data will be used in calculations.

On 19th July 2004 I took all remex from a non-moulting 3y+ female Dunlin, that had been killed by a bird predator. The feathers were inserted in perforated paper and dried at room temperature for two months, finally they were weighed with a Mettler Toledo AB204 to the nearest 0.1 mg.