right sjoerd, Camp Robbers were the Grey Jays! i used to put bread crumbs in my hands and they'd land on my fingers and eat them!
Thanks Eileen--I also thought that the blackbird's songs varied from place to place...but I have no concrete proof. Thank you JEWELL--for your nice words and inquiry. The basic shell is made of calcium carbonate and is white. If birds have coloured eggs, it comes from pigments (green or blue) present during the formation of the shell stage. This propensity can be genetic (carried by the females on the female chromosome) or may take place when the soil in the region where the birds live is calcium-poor. Somehow the bird's body can compensate (there is the possibility of effecting a "Plan B", as it were), which brings us to the subject of speckling. There are also speckled egg shells, as you well know. Apparently the speckling is caused by protoporphyrins (brown or reddish colour pigments). It is thought that these protoporphyrins actually strengthen shells as well as make them less brittle. The amount of protoporphyrin speckles and speckling present on the egg shell is in an inverse proportion to the amount of calcium in the soil. Interesting, eh? Well, speckling can also occur genetically--take for instance birds that lay eggs on the ground--they need camouflage, so they often have speckled eggs. Some birds use the speckling patterns to recognize their eggs when they return to the nest. Well, what I am getting to via this borderline esoteric chatter is to say that I do not think that the base colours are coming from food in the various regions because the egg colour determination is genetic. Having said that, when it comes to speckling, then it certainly is milieu determined-- as we have seen in regions where the soil is calcium-poor. When I was attending uni, I thought that egg shell colour was determined by the food that the birds ate--like feather colour is determined by what a flamingo or a spoonbill eats. Later research proved this to me untrue. The way that I see it is that base colour and speckling are two separate aspects of egg shell variation that may occur individually or combined, but can have two separate mediators. Well Jewell, you didn't ask for all this scientific jabber, but perhaps if the weather there is not good and you don't have anything better to do, you can wade through it. What you will do with the info, I don't know. I have it in my head, but never use it. At any rate, I appreciate your interest in the posting.
