Birds display a fantastic variety of colours, and this is often related to sexual selection. However, colours can also function in crypsis. We are testing hypotheses explaining colour variation by considering avian visual physiology, patterns of variability and sources of colour production. This research program is led by long-term collaborator Kaspar Delhey.

 The effect of colour producing mechanisms on plumage sexual dichromatism in passerines and parrots.
Delhey K & A Peters. 2017. The effect of colour producing mechanisms on plumage sexual dichromatism in passerines and parrots.  Funct Ecol 31:903-914

In a large comparative study, we found that plumage coloured by red carotenoids was more sexually dichromatic. However, colours produced by other mechanisms appeared more or less equally sexually dichromatic.

Conspicuous plumage colours are highly variable.
Delhey K, B Szecsenyi, S Nakagawa & A Peters 2017. Conspicuous plumage colours are highly variable. Proc R Soc Lond B 284: 2016.2593

This paper used fancy stats to show that plumage colours that are strongly contrasting against the background are also highly variable. Exactly why this should be so remains open for debate (and further research).

Conservation implications of anthropogenic impacts on visual signalling and camouflage.
Delhey K & A Peters. 2017. Conservation implications of anthropogenic impacts on visual signalling and camouflage. Cons Biol 31(1): 30-39

This paper documented how anthropogenic environmental changes could result in impaired visual signalling and disrupted camouflage and that this could have conservation implications.

Increased conspicuousness can explain the match between visual sensitivities and blue plumage colours in fairy-wrens.
Delhey K, SA Kingma, ML Hall & A Peters. 2013. Increased conspicuousness can explain the match between visual sensitivities and blue plumage colours in fairy-wrens. Proc R Soc Lond B 280: 20121771.

In fairy-wrens, higher UV sensitivity increases the contrast of UV/blue colours against natural backgrounds, possibly making these colours more attractive. This could provide an explanation why all male fairy-wren species with high UV sensitivity have UV/blue plumage patches

The carotenoid-continuum: carotenoid-based plumage ranges from conspicuous to cryptic and back again.
Delhey K, ML Roberts & A Peters. 2010. The carotenoid-continuum: carotenoid-based plumage ranges from conspicuous to cryptic and back again. BMC Ecology 10:13

We found that depositing carotenoids in the plumage leads to more cryptic plumage and thus may be selected for concealment rather than conspicuousness. This implies that it is not always necessary to invoke signaling in order to explain carotenoid-based yellow plumage.