White morph of the Reddish Egret. (Standard Reddish Egret below.)
If a Labrador Retriever and a Poodle can be interbred to create a “Labradoodle,” why can’t a Cardinal and an Oriole interbreed to form a “Cardinoriole?” Wow! Would that be one colorful bird! Simple answer: all breeds of dog originated from one canine specie and therefore can interbreed to their heart’s content to ultimately create highly individual breeds from Chihuahua to Great Dane, as well as the ever lovable “Mutt.”
Birds, on the other hand, are each members of their own separate species and can only breed within their own specie. Therefore you will never see a “Cardinoriole” or a “Hummingcrane.”
O K, then why are the Great Blue Heron and the Great White Heron (both below, right) considered the same specie, and why are there two colors of Reddish Egret, not to mention Short-tailed Hawk (bottom)? Another simple answer: they are considered color morphs of the same specie, carry the same DNA, and can breed together. With some species, Screech Owls (red and gray morphs) for example, the young of either or both morphs may appear in the same nest. The “why” for this occurrence is still a matter of study among ornithologists, but a very erudite and hyper-technical discussion of the current thinking can be found in this paper on Colour polymorphism in birds: causes and functions.
An over-simplified summary of the different theories would be that:
(Those last two weren’t really in the erudite study, but I think they are probably true.) Since the white morphs of these three species occur most often in the southern most portion of their Florida range, perhaps the white plumage helps keep them cooler. Just a thought.
Maybe instead of getting all bogged down in analyzing why there are color morphs, we should just enjoy the birds and marvel at how they are able to adapt as they see necessary. Incidentally, there are some birds that have been bred within their own specie, much like dogs. Just think of domestic chickens, from White Leghorns to Rhode Island Reds, and all the different colors of pigeons, all descended from the original Rock Pigeon. Sometimes it even happens naturally in the wild: for an example, check out the Wurdemann’s Heron, which is a rare interbreed between the Great Blue and Great White Herons, exhibiting features of both. You can find it in the Green Cay trip report on the St Lucie Audubon web page: stlucieaudubon.org/docs/120204GreenCay.html
Still, a “Cardinoriole” would really be neat. (5/24/2012)