It’s about more than sex
Some will have perhaps noticed the recent dearth of pretty pictures appearing on this Pairodox blog. Indeed, it has been nearly a month since I have been out with the camera; either the weather has been uncooperative or there simply hasn’t been time. Given these unfortunate circumstances I have once again taken to the archive and present here an image taken last spring of one of Joanna’s layer hens. Have you ever marveled at the beautiful flourish of red tissue which adorns the heads and chins of most chickens? Although these may be characteristic of individuals of both sexes the most elaborate adorenments are found among males. If you were to guess that combs and wattles were structures of sexual advertisement and allurement you’d be correct. In addition, however, these elaborate tissues play an equally important, and perhaps primary, role in the regulation of body temperature. Birds are able to maintain a core temperature with metabolic heat and we refer to them as endothermic homeotherms. Other organisms whose body temperature is influenced by and varies with the environment are, in contrast, ectothermic poikilotherms. As such, and as the weather turns cold, birds have the capacity to ramp up their internal fires to keep warm. Unfeathered surfaces, such legs and feet for example, present some difficulty in terms of heat loss and this is especially so for waterfowl. Many birds which routinely have their feet in water (even moving water which may be supercooled) possess a pattern of blood circulation in their lower limbs called counter current exchange in which outgoing arterial blood runs immediately adjacent to incoming venous flow. This apposition of outgoing and incoming supplies cools the arterial blood (thereby preventing loss of heat to the environment) and warms the venous blood (thereby preventing depression of core temperature). Birds will stand alternately on one foot and then the other to reduce contact with the frozen ground. During the warmer months birds will spread their wings to dissipate heat and can often been seen panting to expose wet surfaces of the mouth and throat to allow for evaporative cooling. Other unfeathered surfaces such as the comb and wattles provide expansive surfaces for radiative cooling but are in danger of freezing during the coldest days of winter. When our girls raised show birds they would coat these especially delicate surfaces with Vaseline as a way of providing additional protection from frostbite. And, lastly, did you know that you can determine whether a hen will lay brown or white eggs by looking at the color of her ear lobes (the patches of pigmented skin in back of and below the eyes)? The general rule is that if she has red lobes (like the girls shown here) she’ll lay brown eggs, and if she has white lobes she’ll lay white eggs. It’s always interesting to me that animals make such reasonably good sense.
The comb types shown are classified as (left to right and top to bottom)
Strawberry, Buttercup, V-Shaped, Pea, Cushion, Single, Walnut, and Rose.
[The source for the beautiful line drawings is TBN Ranch.]