In part 1 of this 6 part series, we learned what pheasants were up to during May and June. We discovered how pheasants can overcome low annual survival by exhibiting high reproductive potential through large clutch sizes and multiple re-nesting attempts if previous nests are destroyed.
May is the peak egg laying month while June is the peak of hatch for pheasant nests. Hens have invested vast amounts of energy into egg production and brood rearing responsibilities by the end of June. Their body weight and condition plummet during this time because food intake can not keep up with the energy demanding responsibilities of motherhood. Newly hatched chicks are targeting insects for most of their diet during June because a protein rich diet is needed to grow feathers and tissue. Roosters spent most of May and June displaying to attract hens, but this activity peaked in April and is nearly complete by early July.
Now the dog days of summer are here. Nearly all hens are done nesting and those who had successful nests continue to lead their broods to areas with succulent forbs where chicks can forage on insects. The roosters’ breeding responsibilities are nearly complete until next spring. One may think July and August should be a cake walk for pheasants with the most energy demanding time of the year behind them. This is true for roosters, but hens have their most challenging days ahead in July and August. Chicks are not out of the woods either. Many will be killed by predators or farm machinery and the remaining chicks need to gorge on insects and seeds to gain weight before fall. As we all know, winter can come awfully early in South Dakota.
So why can roosters lazily coast through July and August without a care in the world, while hens struggle to survive? Summer responsibilities for roosters are quite simple. Finish the molt that was started in late June and start preparing for winter by gaining weight. Roosters have been losing weight for 5 months and may weigh 15% less than they did during mid-winter. Since courtship and breeding responsibilities dwindle by July, roosters can take advantage of abundant food resources and replace all their feathers and gain modest weight in July. Rate of weight gain increases in August as energy is no longer needed to grow replacement feathers. July and August are quite relaxing for rooster pheasants in South Dakota. As roosters are taking advantage of rich food resources to molt and gain weight, most hens are attending to broods and beginning their molt in July. Hens molt after egg laying and incubation because completing all three at the same time would be too energy demanding. While roosters can focus all efforts on molting and gaining weight, hens have energy demanding brood rearing duties. Hens must lead broods to habitats rich with insects and keep them out of harms way be keeping an eye out for predators (Pictures 1 and 2). She has already lost 20% of her body weight since April and brood rearing and molting activities in July could cost her another 10% of her body weight. She can not take in enough energy to cover these highly energy demanding tasks.
Hen pheasants are in their poorest physical condition in August during most years and could weigh 30% less than before egg laying began. Only during years of extreme winter weather would a hen pheasant be lighter in March than in August. They must reverse the trend of losing weight as death occurs when 40% of her body weight is lost. August is a critical time for hens as their stressed bodies are more vulnerable to disease and parasites. Hen survival during August can be lower than during winter.
There are several factors that affect just how stressed (loss of body weight and body fat) hens become in August, and not all factors are obvious. This is important since survival is highly dependant on how stressed hens become during late summer. First, when the hen was hatched the previous year influences her condition going into winter and ultimately the next spring and summer. If a hen was raised from a late hatching nest due to weather or predation of early nests, she will be lighter going into winter than early hatched hens. This hen will be lighter and in poorer condition than early hatched hens during the following August.
How many eggs a hen lays during spring can influence her body weight by late summer. Cold and wet weather can delay nesting, but egg production is based on length of day. Hens begin producing eggs whether the weather is ideal for nesting or not. Eggs produced during inclement weather are “dumped” in nests of other birds (other pheasants, grouse, ducks, and etc.) or even on the ground. Hens forced to re-nest due to predated nests also produce more eggs. Obviously, hens that produce fewer eggs during spring will be in better condition by late summer.
Additionally, the previous winter can influence hen condition during spring and summer. As more body fat is used to keep warm during winter, less is in reserve for egg production during spring. Areas with better winter cover yield heavier hens in spring which can influence egg production and hen survival during summer. Who thought winter habitat was so important to pheasants during spring and summer!
Besides these factors, pheasants are also stressed by extreme summer heat. As long as temperatures stay under 102°F, pheasants can stay cool by limiting activities to morning and evening and by utilizing shade during mid day (Picture 3). As temperatures rise above this critical value, pheasants must pant similar to a dog to stay cool. This behavior, called gular fluttering requires additional energy (which produces heat) but the process removes more heat than it produces. As you can see, these heat stress days can require energy at a time when pheasants do no have a lot to spare.
July and August is also a critical time for chicks. They are tasked with gorging on insects and seeds to grow tissue and feathers while avoiding predation. Half of pheasant chicks will not survive until fall due to predation or farm machinery. While adults molt once during summer, chicks actually molt twice. By early July, chicks have replaced their down with hen-like flight feathers. In early August, chicks begin a post juvenile molt to replace their juvenile feathers with their adult plumage. By 17 or 18 weeks of age, pheasant “chicks” resemble adults in plumage.