The Heat’s Effect on Game Bird Management
By: Justin Bryan
Without a doubt, heat can take a toll on wildlife. This year in Texas, spring and summer started with about ideal conditions in regards to the weather for all wildlife. Plenty of cloud cover and consistent rainfall, played a major role in keeping temperatures from soaring and creating adequate amounts of vegetative food and cover. But as usual all good things must come to an end and it did, abruptly. Those cool and moist days were soon replaced by days, weeks, and now months of temperatures in the high 90’s to 100’s. Characterized by very little cloud cover and a consistent dry southwest wind. For wildlife such as bobwhite quail and turkey, which are ground nesting birds, the heat can be a disaster in regards to nesting success and game bird management efforts.
Bobwhite quail are documented physically shutting down at temperatures around 104o F…in other words hyperthermia sets in. While their eggs have shown to become inviable at about 120o F. In addition, quail chicks lack the ability to thermoregulate. Turkey are much the same. Some research has shown that the bald head of a turkey not only plays a role in the breeding display process but may actually help in thermoregulation during these hot summer days. This is important to understand and think of when looking at your game bird management plans.
It just so happens my kids have a two Rio Grande hens and a tom that stay around our house outside of town. Interestingly, one of the hens nested in February, in heavy cover and hatched 12 poults. She had ideal nesting conditions…cool temperatures, consistent rainfall and heavy overhead brush cover that was more limb structure than leaf structure.
The second hen, began nesting in early July….just as the rainfall and cool temperatures abruptly shut off. This hen decided to nest in an area where we had a large patch of “volunteer” pumpkins growing. Early in the nesting, the pumpkins were able to maintain leaf structure with the abundant rainfall but as the days and amount of heat increased and rainfall decreased the pumpkins wilted and finally died. This hen went from substantial overhead protection from predators and the sun to basically sitting in the direct sunlight all day and no protective cover. On a side note, the second hen and tom decided to sit with her through the entire incubation period (~28 days).
I assumed the nest would fail due to their lack of hiding and thermal cover. I finally felt sorry for the hen and built a quick overhead structure to try and provide the her with some kind of shade throughout the day. Interestingly, she kept setting but the number of eggs present continued to decline…I assumed they were inviable and breaking. Finally, with a few days of nesting till hatching should occur, she had 3 eggs left. I decided with the use of an infrared temperature gun to take a few readings to find out just how hot these birds and their surrounding were getting each day through the nesting time. Below are the results from one afternoon with 70% cloud cover. The turkey themselves were the only location in some sort of shade all other reading were taken in direct sunlight.
Time (p.m.) Air Temp. Grass (6” height) Bare Ground Turkey Ext. Feathers Concrete
2 95 118 124 104 118
3 98 125 125 111 123
4 99 125 125 117 121
5 98 122 126 114 115
6 98 100 101 99 108
Amazingly the three remaining eggs did hatch the day I acquired these temperatures. Unfortunately, both the tom and two poults were predated upon that night by coyotes
This isn’t hard science but it does emphasize the importance of providing quality habitat. Ground nesting birds have to have sufficient nesting cover (tall warm season grasses and roughly 15% brush cover) for not only overhead and surrounding protection from predators but from the unrelenting heat of the sun. I’ll give credit to Dale Rollins, as he says, “a rancher with bird dogs is a quail’s best friend.”
Range and ranch management, proper grazing and brush management, is the key to a successful livestock and wildlife operation. A healthy rangeland…desirable healthy grasses, forbs, and brush will always be the key to our successful game bird management programs, and for all wildlife and livestock, during times of abundant rain and during droughts.