Study: Eggs are darker in cold climates
Birds living in cooler climates lay eggs that are on average darker than those from warmer regions.
The dark coloration of eggs helps keep them warmer in sunlight. To develop properly, the bird embryo inside the egg must always be at the right temperature. In cold regions, eggs cool down quickly when the parents leave the nest, for example to search for food. The dark coloration can help keep eggs at temperature for longer, researchers report in the journal «Nature Ecology & Evolution».
The scientists led by Daniel Hanley of Long Island University (USA) had examined the brightness and color of eggs from 634 bird species . They found the eggs in the collections of natural history museums. They then linked the egg color to the geographic breeding range of each bird species.
Birds that build ground nests lay darker eggs
Eggs in regions with low temperatures and solar radiation are therefore often significantly darker. This is especially true for those bird species that build open nests on the ground. Eggs from cup-shaped nests or nests in cavities, on the other hand, sometimes deviate from this pattern.
Dark eggs as a trick for better heat retention
To get to the bottom of the color distribution, Hanley and his colleagues exposed various eggs to sunlight. Darker eggs heated up faster than white eggs and also stayed warm longer. The dark color is therefore probably a trick for better heat retention in cold climates, according to the researchers.
More on the subject of recreational hunting: In our dossiers on recreational hunting gather fact-checks, analyses and background reports. The scientific evidence is presented in the overview Studies on the Effects of Recreational Hunting.
The position of IG Wild beim Wild: IG Wild beim Wild rejects recreational hunting. Our model is the canton of Geneva, which has managed without recreational hunting since 1974: without hunting seasons, without hunting dogs, without driven hunts, without high seats, without the animal cruelty and crime that go hand in hand with hunting season elsewhere. What has worked there for over fifty years disproves every position paper by JagdSchweiz. An association that bases its policy on claims it refutes in its own documents is not a professional organisation, but a factory for misinformation.
