Plumage development and visual communication in the Greater Kestrel Falco rupicoloides near Pretoria, South Africa

Abstract

Kemp, A. C. 1999. Plumage development and visual communication in the Greater Kestrel Falco rupicoloides near Pretoria, South Africa. Ostrich 70 (3&4): 220–224.

I trapped, marked, sexed and examined moult and softparts on 101 free-living Greater Kestrels Falco rupicoloides near Pretoria, South Africa, during 1975–1988.1 collected and plucked one kestrel to determine the number and mass of its feather tracts, as an index of materials invested in moult. I also examined moult on 72 museum specimens from southern Africa and observed plumage and softpart changes in four captive birds. During 1975–1979,1 made focal observations on free-living adult kestrels (males 181 h, females 262 h) and recorded monthly samples of their visual communication behaviours to the nearest minute.

Greater Kestrels can be aged for three successive plumage and softpart stages (juvenile, post-juvenile, adult). Plumage changes with potential signal effects involved only small investments at the post-juvenile and first adult moults (3.7% and 11% of total plumage mass respectively). Changes in colouration and communication behaviour correlated with relevant stages of the annual cycle, possibly to miminze conflict with territorial adults and age of first breeding. Remex and rectrix moult starts on average much later in relation to egglaying for Greater and some tropical kestrels than for some temperate species. This and other individual variation in timing may result for variations in nutritional status.