Dressed for Success

Why is it that some animals evolve to be as uncamouflaged as possible? Display colouration and plumage for sexual selection seems to be more important in some avian species that the need to be hidden from predators. Does that mean the these species are immune to the danger of predation? Or simply that passing on the genetic heritage is a more important factor to be dealt with before death by whatever means?

Flocking behaviours do reduce the likelyhood of any one individual becoming prey through shared vigilance and flock distraction behaviour, but not all birds that exhibit these attractive displays are social creatures.

For example the Cassowary in a flightless bird that lives in a forested environment in the Tropics of Australia and New Guinea. The male has an amazingly colourful head with a crest on the top of his skull. There are few natural predators to this species and, as discussed previously, it is well protected. The bright colour increases the chance that a potential mate will see him through the dense foliage, and also bears striking colour similarity to some of the Cassowary's favourite food.

Our little Blue Wren is dressed in a similar colour, but not to match food this time. His bright colour is a signal to his family and is obvious to any potential interloper that this is a "taken" group of females. the only times I have seen a second male with the groups around here is when a young male is almost completely decked out in his adult colouring - I haven't seen any visiting males, nor the moment when the young male is sent from the group.

Quite often there is a colour difference between the male and female of the same species as you can see above with the blue wrens and below with the Red-rumped Parrot. Until recently I thought that the bright male was the only option and that females were never more colourful than their companions, however there are apparently a few species like the Eclectus Parrot that break this rule.

The brightest local bird is probably the Crimson Rosella, a stand-out against all the local foliage. These birds are usually found in pairs or as a flock of juveniles (with slightly different colouration).

Given that the feathers I found when following the Sparrowhawks (see Predators 2) were brightly coloured, and that there is never an absence or obvious fluctuation in the numbers of these brightly coloured birds, their breeding must be successful enough to maintain a stable population.

So what can we draw from this for our reconstructions of the Dinosaurian ancestors? We have found many species that exhibit physical sexual dimorphism in their physical forms - particularly the crested Hadrosaurs and horned Ceratopsians. It is also a possibility that dinosaurs came in the same spectrum of colours as birds do today. It is not necessary for them all to have been uniform grey like elephants or camouflaged like many birds. Bright displays of colour are plausible for dinosaurs too, although there is yet to be fossil evidence to support them being as bright as the Blue Wren or Rosella. We do some evidence from dinosaur feathers to support colour variation across the body including stripes and different colours in different body areas.