The killdeer (Charadrius vociferus) is a medium-sized plover found throughout much of North America. These birds are known for their distinct plumage, loud vocalizations, and elaborate broken-wing displays used to distract predators from their nests. Killdeer are ground-nesting shorebirds that lay their eggs in shallow scrapes in open fields or gravelly areas. A key question many birders and researchers have is: how many times a year do killdeer lay eggs? Let’s take a closer look at the breeding biology and nesting habits of these fascinating shorebirds to find the answer.
Killdeer Breeding Season and Nesting
Killdeer have an exceptionally long breeding season compared to other shorebirds. While the exact timing varies by location, they typically begin courting and establishing breeding territories in early spring. Egg laying starts in mid-March in their southern range and may extend all the way into late August or September in the northern parts of their range.
Most killdeer have two clutches per season, meaning they lay their eggs two times per year. The first clutch is typically initiated between mid-March and mid-May depending on latitude. If this clutch fails due to predation, flooding, farming activity, or other disturbance, the pair will re-nest and lay another clutch of eggs. This second clutch occurs from late April through July. Further north, the season is more condensed with egg laying mainly between May and July.
Killdeer nests are simple shallow scrapes or depressions in open gravel areas, often lined with pebbles or fragments of debris. The female usually lays 3-6 eggs per clutch. Given the length of the breeding season and tendency to re-nest, a mated pair of killdeer may produce up to 12 eggs a year from two separate clutches. However, an average of 4-8 eggs per year is more typical.
Clutch Size and Re-nesting Behavior
As mentioned above, killdeer clutches contain anywhere from 3-6 eggs, with 4 eggs being typical. The female alone incubates the eggs for 22-28 days until they hatch. During incubation, the nest and eggs are very vulnerable to predators and external threats. As a result, it’s common for the first clutch to be lost.
When this happens, the mated pair will often re-nest and lay another replacement clutch within 1-2 weeks. This persistence allows killdeer to maximize their total number of eggs laid per season despite external factors. Their re-nesting behavior is a key reason why they are able to lay eggs multiple times per year.
Multiple Broods in a Season
In addition to re-nesting after failed first clutches, some killdeer are able to raise multiple successful broods per season. The term “brood” refers to a group of hatchlings.
After a successful first nest, some pairs will initiate and complete a second nesting attempt while still feeding the young of their first brood. This results in fledging two separate broods in the same year. However, this pattern is more common in the southern portion of their range and late in the breeding season when more daylight time allows for successfully raising multiple broods.
Farther north, the shorter spring and summer season means most killdeer raise just one brood per season, even if they laid two clutches of eggs. The ability to double brood and fledge young twice in one year allows southern killdeer pairs to lay and hatch a substantially higher number of eggs annually.
Geographic Variation in Nesting Frequency
When looking at the total number of clutches or eggs laid per year, there is considerable variation across the killdeer’s extensive range. Their nesting habits and length of the breeding season differ significantly between northern and southern regions.
In Florida, Texas, and coastal southern states, killdeer may lay eggs from as early as February through August. These southern birds have a prolonged season and more time to lay multiple clutches. Pairs often lay two complete clutches, and will readily re-nest up to 2-3 more times if a clutch is lost. In certain cases, they even raise two broods in one year.
In contrast, the breeding season is much shorter in northern states like Minnesota, Maine, and Alaska. Up north, egg laying typically occurs only between May and July. The compressed window means northern killdeer frequently raise just one single brood per season, even if they lay two clutches. Double brooding is rare.
These differences mean the total number of eggs laid per year can range from 4-6 eggs in northern birds to 8-12 eggs for southern killdeer in places like Florida and Texas. Coastal populations tend to lay more eggs than those further inland as well.
Impact of Habitat and Food Availability
In addition to geographic location, the local habitat and food supply impacts how many eggs killdeer are able to lay.
Killdeer thrive in open habitats with gravel areas, short vegetation, and sparse ground cover for nesting. They prefer landscapes with a mix of bare gravel substrates near foraging sites like shorelines, pastures, crop fields, golf courses, gravel roads, and disturbed settings.
In prime habitat with abundant food, breeding pairs are able to lay eggs early, easily find nest sites, and raise multiple broods. However, if the habitat is degraded or food is limited, they may lay fewer eggs or struggle to hatch successful clutches at all.
For instance, killdeer nesting in ideal golf courses or wetland habitats lay more eggs per year than those relying on marginal agricultural lands or industrial areas with minimal foraging options. Habitat alteration and expanding development has reduced productive nesting sites for killdeer in many regions.
Age and Experience
The age and breeding experience of pairs may also influence annual egg production. Older, more seasoned pairs tend to lay larger clutches and are more likely to re-nest and raise multiple broods compared to younger first-time breeders.
Younger killdeer breeding for the first time usually lay just 1-2 clutches of 3-4 eggs in a season. Older birds with several years of breeding experience are able to find prime nest sites, lay more eggs per clutch, double brood, and replace failed nests more readily. Their reproductive success improves with experience.
Banding studies show killdeer can live 13 years or more in the wild. These older experts may lay twice as many eggs per year as inexperienced first-time nesters.
Threats to Nest Success
While killdeer lay many eggs, their nesting success rates are variable across sites and often fairly low overall. Nest failure is actually quite common in this species.
This is due in large part to their habit of nesting right on open ground, which leaves eggs and young extremely vulnerable. Nests are threatened by farming activities, vehicle traffic, livestock, dogs, flooding, and myriad predators. Documented nest predators include coyotes, foxes, skunks, raccoons, crows, gulls, snakes, and others.
Since clutch loss is frequent, the persistence of killdeer in re-nesting enables them to lay eggs multiple times despite regular nest failure. Without their resilience in starting new clutches, seasonal egg production would be far lower.
Estimates indicate only 30-70% of killdeer nests successfully hatch, depending on the study location. These low hatching rates necessitate continually laying new clutches to compensate.
Conclusions
To summarize key points:
- Killdeer typically lay eggs 2 times per season (range: 1-3 times) from 2 separate clutches
- Average clutch size is 4 eggs (range: 3-6)
- Total eggs laid per year averages 4-8, but may reach up to 12
- Southern killdeer lay more eggs than northern birds per season
- Ideal habitat and food supply enables higher egg production
- Older birds lay more eggs than younger first-time breeders
- Frequent clutch loss necessitates re-nesting and multiple clutches
In conclusion, most killdeer lay eggs twice per year, with two clutches of 3-6 eggs each from the same breeding pair. The total number ranges from just a few eggs among young birds and northern pairs to up to one dozen eggs laid annually by experienced southerly pairs nesting in prime habitat. Their resilience in re-nesting frequently allows high seasonal egg production despite the risks. Understanding details of killdeer breeding biology provides key insights into the lives of these remarkable shorebirds.
References
- Jackson, B. J., & J. A. Gerwin. 1996. Breeding ecology of the Killdeer in southern
Illinois. Transactions of the Illinois State Academy of Science 89:73-80. - Jorgensen, J.G. 2012. Birds of the Rainwater Basin, Nebraska. Nebraska Game and Parks Commission Lincoln, NE.
- Kaufmann, G.W. 1996. Ecology and behavior of Killdeer in cultivated fields. Dissertation. Purdue University, West Lafayette, Indiana, USA.
- Kaufman, K. 2005. Kaufman Field Guide to Birds of North America. Houghton Mifflin Harcourt.
- Rousseau, P., Gregoire, A., Visser, J., & Bêty, J. 2014. Fighting in the snow: mating system drives contest dynamics in the territorial killdeer Charadrius vociferous. Animal Behaviour, 90, 153-164.
- Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link. 2017. The North American Breeding Bird Survey, Results and Analysis 1966 – 2015. Version 2.07.2017 USGS Patuxent Wildlife Research Center, Laurel, MD
