By Travis Runia, GFP Senior Upland Biologist
Editor’s Note: This excerpt is from a six-part series on pheasant ecology written by Travis Runia, senior upland biologist for the South Dakota Game, Fish and Parks Department. The series was originally written for the South Dakota Conservation Digest and is reprinted here with permission. To read the entire pheasant-ecology series by Runia, or to read the South Dakota Conservation Digest online, go to gfp.sd.gov.
With pheasant season still a few months away, pheasants are one of the last things sportsmen are thinking about during spring. However, the nesting and brood-rearing season of May and June represents one of the most critical times for pheasant populations.
Pheasants are short-lived birds, with annual survival averaging only 50 percent. During severe winters, survival can be much lower in areas containing marginal or inadequate winter habitat. With such low survival, how do pheasants sustain such high populations each fall?
Of all upland game birds, pheasants exhibit one of the highest reproductive potentials, thus enabling them to bounce back after severe losses in short time periods when provided adequate nesting habitat. Despite this, pheasants still rely on quality nesting and brood-rearing habitat to recruit new birds to the fall population.
The nesting season begins in late April as hens seek out attractive nesting cover usually consisting of undisturbed grasslands such as lands enrolled in the Conservation Reserve Program (CRP). Most hens initiate their first nest during the first half of May, but this can be delayed by unseasonably cold or wet weather.
At the same time, male pheasants have spent the past month establishing and maintaining territories across the landscape. Crowing and wing-flapping behavior aimed at attracting females peaks in April but continues through June to serve hens that are re-nesting.
After courtship, hens lay one egg per day until a full clutch of 10-12 eggs is reached. During the next 23 days, hens will spend 23 hours per day incubating the eggs and leaving for only short intervals for limited amounts of food and water.
Egg laying and incubation are extremely energy demanding, and during this incubation period a hen’s food intake is low. Hens can lose 75 percent of their body fat and 10 percent of their body weight in just one month. If not challenging enough, only about 25 percent of nests are successful in large blocks of undisturbed grasslands, and success has been documented much lower in linear and fragmented habitats which are generally smaller in size and are more vulnerable to mammalian predators.
Fortunately, pheasants almost always re-nest if previous nests are destroyed and may initiate up to four nests in a single season. Because of the energy demands of producing and incubating eggs, clutch size and egg size decrease for each subsequent nesting attempt. If a third nesting attempt is initiated, the clutch size could be as low as five or six eggs. Even with low success of each individual nest, 70 percent of hens may pull off one successful nest through multiple nesting attempts.
Hatching a successful clutch is only half the battle to recruit pheasants to the fall population. Pheasant chicks are precocial, meaning they hatch with eyes open and are able to leave the nest and feed themselves within one day of hatching.
Cold snaps in June can greatly decrease chick survival. It has been documented that 1- and 2-day-old chicks exposed to 43 degree temperatures die after 30 minutes of exposure. Susceptibility to the cold quickly decreases with age, and by 11 days of age the chicks can fully regulate their body temp.
As stated earlier, pheasants are attracted to undisturbed grasslands for nesting sites, such as land enrolled in CRP. But does this same habitat provide for the needs of pheasant chicks? This depends on the structure and composition of the grassland.
Ideal brood-rearing habitat provides abundant insects, aerial concealment and allows movement at ground level by small chicks. The average grass field which has not been disturbed recently and lacks diversity does not meet these criteria. Can you imagine a tennis-ball-sized pheasant chick navigating through thick 7-foot-tall grass that your Labrador struggles to get through during the fall?
Pheasant chicks primarily eat insects during the first one to two weeks of life because they are high in protein. Protein functions as building blocks to form muscle tissue and feathers that allow for rapid chick growth.
Without plentiful insects, growth rates and survival of chicks can be greatly reduced. As a result, hen pheasants will often move their broods great distances to find suitable brooding habitat such as “weedy” areas. Broadleaf plants act like insect factories, while also providing aerial concealment without impeding chick movement at ground level. Aerial concealment protects chicks form aerial predators and provides shade during hot summer days.
Even when good habitat is available, it is not uncommon for one-third of the chicks to die, with predators, extreme weather and farm machinery representing the highest mortality factors.
South Dakota is fortunate to have an abundance of high-quality nesting and brood-rearing habitat that allows pheasants to reach their high reproductive potential. As you head to the field each year, remember that what pheasants were doing in May and June has a huge influence on what you will see each fall.
By the time the dog days of summer are here, nearly all hen pheasants are done nesting, and those that 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 cakewalk for pheasants, with the most energy-demanding time of year behind them. This is true for roosters, but hens have their most challenging days ahead in the summer months. Chicks are not out of the woods, either, as 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 the Dakotas.
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, as all they really have to do is finish the molt that started in late June and start preparing for winter by gaining weight.
Roosters have been losing weight for five months and may weigh 15 percent less than they did during midwinter. 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. That all adds up to the fact July and August are quite relaxing for roosters.
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 demand too much energy.
While roosters can focus all their efforts on molting and gaining weight, hens have energy-demanding brood-rearing duties. Hens must lead their broods to habitats rich with insects and keep them out of harm’s way by keeping an eye out for predators.
On average, hens have already lost 20 percent of their body weight since April, and brood-rearing and molting activities in July could cost them another 10 percent of total body weight. Hens simply cannot take in enough energy to cover these tasks at the same time.
Hen pheasants are in their poorest physical condition in August during most years and could weigh 30 percent less than they did before egg laying began in May. Only during years of extreme winter weather would a hen be lighter in March than in August. They must reverse the trend of losing weight as death occurs when a hen loses 40 percent of 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 fat) hens become in August, and not all factors are obvious. This is important since survival is highly dependent on how stressed hens become during late summer.
First, when the hen was hatched the previous year influences her condition going into winter and, consequently, 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. In other words, a hen from a late hatch 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, 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 higher quality 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 temps stay under 102 degrees, pheasants can stay cool by limiting activities to morning and evening and by utilizing shade during midday.
As temps 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 not have a lot to spare.
Summer is also a critical time for chicks. They are tasked with gorging on insects and seeds to grow tissue and feathers and avoid predation. Half of pheasant chicks will not survive until fall due to predation or mortality from 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 being a post-juvenile molt to replace their juvenile feathers with adult plumage. By 17 or 18 weeks of age, pheasant “chicks” resemble adults in plumage.