Why do birds eggs have different colours or patterns?
EcoTraining Instructor Ross Hawkins spends most of his time instructing on Trails Guide or Wilderness Trails Courses, so being on foot most of his day he does tend to see things on the ground level a bit more than those who are in the game drive vehicle. Small things such as birds nests and eggs sometimes get lost do to their camouflage, and there is a reason behind that.
So, why do eggs have certain colours or patterns?
Bird eggs can come in different shapes, sizes and some also have different colours. Just like anything else in the wilderness, there is a reason behind this occurrence. Have you ever stopped to wonder why certain eggs have colours? In this blog, we will explain why.
Depending on where the egg has been laid, the main reason is to ultimately camouflage the egg from potential predators. The more vulnerable the eggs are to predators such as location, habitat, nest exposure, etc. the more elaborately coloured they will be.
This feature is very noticeable in ground-nesting birds. As in most ground-nesting families, the nest is a simple scrape in the soil and the eggs are laid in this small depression and maybe a few pieces of debris might be added to help conceal the eggs, such as animal dung, stones, twigs, etc. The eggs need to then be virtually invisible to all potential enemies.
African Skimmers “lay eggs directly on sandy, shelly, or stony ground, usually on islands or remote beaches that have at least a little vegetation. Some nest in the higher parts of saltmarshes. They often nest near or among tern colonies, which (despite numerous squabbles) can provide benefits, as terns aggressively attack gulls and mammals that prey on eggs and chicks.” – All about Birds
How does this camouflage happen?
This camouflage is by a means of pigmentation which takes place during the process of when the bird lays the egg. The egg will pass through pigmentation glands and the colours obtained will be synthesised from various metabolic compounds such as blood, bile and melanin, these adorn the shell with various colours such as shades of red, brown and blue. Depending on how the glands secrete these pigments the egg will be speckled or maybe spotted or even have wavy lines and as the egg passes down the oviduct of the bird the gland will release pigments in a gradual process. These pigments dry on contact with air and when the egg is finally laid the end result is a near-perfectly camouflaged egg.
On a side-note, birds eggs from colder parts of the world tend to be darker in colour than birds eggs from warmer parts of the world, this is due to the darker eggs being able to absorb more heat in cold climates and the lighter coloured ones enabling the reflection of heat in warmer areas.
Did you spot the Skimmers eggs?
How incredible is this for camouflage!
The next time you come across a spotted or colourful egg, always remember that it is nature’s way of protecting their offspring.
Want to learn more about birds? Why not try our EcoTraining Waterbird Quiz!