New Zealand Journal of Zoology abstracts

---

Is plumage darkness in the North Island robin (Petroica longipes) mediated by aggression?

Å. Berggren

Ecology Group
Massey University
Private Bag 11222
Palmerston North 4442, New Zealand

Present address: Department of Ecology,
Swedish University of Agricultural Sciences,
PO Box 7044, SE-75007, Uppsala, Sweden.
Asa.Berggren@ekol.slu.se

Abstract The extent of darkening of melanin-based plumages in birds has previously been linked with increasing aggressive encounters between individuals. The North Island robin (Petroica longipes) is a territorial New Zealand endemic passerine that displays delayed plumage maturation (darkening of the plumage with age). Aggressive boundary interactions in the robin are relatively common during the breeding season, when territories are protected and juveniles are dispersing. This study tests the hypothesis of aggression-mediated plumage darkening in a population of North Island robins by examining if males and older (darker) birds are either (1) involved in a higher number of aggressive interactions, or (2) are more often the aggressor than females and younger birds. When sex and age are accounted for, darker individuals will be either (3) involved in a higher number of interactions or (4) more often the aggressor in encounters with other individuals. Data were collected by scoring the plumage darkness of 32 individuals in the field, and observing (1) interaction behaviours, and (2) age and sex of the birds involved in each interaction. The results show no support for any aggression-mediated plumage darkness in the robin; males and older birds were not involved in more aggressive interactions, and were not more often the aggressor; and neither the frequency of interactions or the number of aggressive interactions were correlated with a darker plumage. Other more complex mechanisms may explain delayed plumage darkness in the North Island robin.

Keywords aggressiveness; DPM; delayed plumage maturation; melanin; North Island robin; Petroica longipes; plumage darkness; status-signalling

PDF file of entire paper: Print-quality (709K) | screen-quality (326K)

Z08012; Online publication date 24 September 2008
Received 29 March 2008; accepted 17 July 2008

New Zealand Journal of Zoology, 2008, Vol. 35: 331–334
0301–4223/08/3504–0331 © The Royal Society of New Zealand 2008

---

This year's abstracts | Journal home page | All abstracts | Publishing home page