Thread by @TZBirder, Today's #BirdsAtTea is the Bateleur. This colourful relative of the snake-eagles is [...]

Colin Beale

TZBirder

Today's #BirdsAtTea is the Bateleur. This colourful relative of the snake-eagles is widespread but fast declining across much of Africa (another @IUCNRedList are considering uplisting). Adult back panels come in 2 morphs, chestnut (common) and cream (rarer). Why? 1/5 #ornithology

In fact, many raptors have colour morphs and the reasons are varied. Some are themselves adaptive: @arjundevamar's team have done great work showing that black morph Great Sparrowhawks bring more food in shadier places, and white ones in bright sites https://onlinelibrary.wiley.com/doi/pdf/10.1111/ele.12606 2/5

Dark morphs of many raptors are commoner in damp forests, where it is proposed the extra melanin in feathers may protect them from rotting https://bioone.org/journals/The-Auk/volume-121/issue-3/0004-8038(2004)121[0652:FAAFS]2.0.CO;2/FEATHERS-AT-A-FINE-SCALE/10.1642/0004-8038(2004)121[0652:FAAFS]2.0.CO;2.full! But direct benefits in different places seem unlikely for Bateleur & many other polymophic #birds. 3/5

R Eggert

Dark morphs of many raptors are commoner in damp forests, where it is proposed the extra melanin in feathers may protect them from rotting https://bioone.org/journals/The-Auk/volume-121/issue-3/0004-8038(2004)121[0652:FAAFS]2.0.CO;2/FEATHERS-AT-A-FINE-SCALE/10.1642/0004-8038(2004)121[0652:FAAFS]2.0.CO;2.full! But direct benefits in different places seem unlikely for Bateleur & many other polymophic #birds. 3/5 R Eggert

For these it seems more likely that the gene altering colour is located on a chromosome very close to something else, which is what evolution works on: in owls grey morphs can be more temperature sensitive than brown ones https://www.nature.com/articles/ncomms1213/ by genetic linkage 4/5

D Peterson

For these it seems more likely that the gene altering colour is located on a chromosome very close to something else, which is what evolution works on: in owls grey morphs can be more temperature sensitive than brown ones https://www.nature.com/articles/ncomms1213/ by genetic linkage 4/5D Peterson

So the colour morphs of #birds like the Bateleur are unlikely to affect survival directly, but may be linked to another gene that is under selection in different ways in different environments. Cream morphs are slightly commoner in drier landscapes, so maybe? 5/5

@paulolivertz

So the colour morphs of #birds like the Bateleur are unlikely to affect survival directly, but may be linked to another gene that is under selection in different ways in different environments. Cream morphs are slightly commoner in drier landscapes, so maybe? 5/5 @paulolivertz

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