The killdeer (Charadrius vociferus) is a medium-sized plover found across most of North America. These birds are known for their loud, piercing “kill-dee” call which gives them their name. Killdeer are active and noisy birds that can be seen foraging in open fields, gravel roads, parking lots, and shorelines during the day. But are killdeer also active at night? In this article, we’ll take a closer look at killdeer behavior to find out if these birds are nocturnal or diurnal.
Killdeer Natural History
Killdeer belong to the diverse order Charadriiformes, which includes plovers, lapwings, and sandpipers. They are one of the most widespread shorebirds in North America. Some key facts about killdeer natural history:
- Medium-sized plover with adults reaching 8.5-11 inches in length and 5.5-5.7 ounces in weight
- Distinctive black breastband, white undersides, brown back and wings
- Long tail and legs for a plover
- Pink legs and red eyerings
- Loud, ringing “kill-dee” call
- Prefers open habitats near water – shorelines, fields, gravel roads
- Nests on the ground in scrapes, usually with 4 speckled eggs
- Both parents incubate eggs and care for precocial young
- Feeds on insects, worms, crustaceans, seeds
- Migrates south in winter across most of range
Knowing some background on the natural history of killdeer gives us clues about when they are active. Next, we’ll look at some specific evidence for killdeer activity patterns.
Evidence of Killdeer Activity Patterns
Several lines of evidence indicate whether killdeer are active at night or strictly diurnal:
Observation of Foraging Behavior
Killdeer are most frequently observed foraging during daylight hours. Their foraging behavior includes running across open ground and stopping to pick at food items, open-ground probing, and picking items from shallow water. This activity pattern matches their habitat preferences for open fields and shorelines, where visibility is better during the day. Low-light or nighttime conditions would make foraging more difficult for these visual hunters.
Calls and Displays
The killdeer’s loud calls and distraction displays are used to defend nesting territory and are primarily given during the daytime in the breeding season. These visual displays would be less effective at night when visibility is limited. The killdeer’s most intense calling peaks at dawn and dusk but drops off significantly after dark.
Circadian Rhythm Studies
Researchers have studied circadian rhythms in shorebirds and found that killdeer exhibit diurnal patterns of activity. Their body temperature and metabolism rises during daylight hours and falls during the night. This circadian rhythm suggests they have adapted as a diurnal species.
Timing of Egg Laying and Incubation
Killdeer nesting behavior also suggests diurnal activity. Egg laying and incubation duties are carried out during daylight hours, indicating the killdeer are active in the daytime during breeding season.
In Depth Look at Killdeer Nocturnal Behavior
The evidence overwhelmingly suggests that killdeer are primarily active in the daytime. However, there are some observations of possible nocturnal behavior that merit a deeper look:
Low Levels of Nighttime Calling
While peak vocalizations occur at dawn and dusk, killdeer will occasionally make some calls at night. This may happen more often during nesting season or on brightly moonlit nights when visibility is better. Their nighttime calling is significantly less frequent and softer in volume compared to daytime.
Nocturnal Migration
A few studies of nocturnal migration using radar reference killdeer as occasional nighttime migrants. Their migration flights typically happen around dusk, dawn or moonlit nights. Not all individuals migrate at night and night flights are usually shorter in duration compared to diurnal migration.
Nighttime Feeding
In a few instances, killdeer have been observed foraging at night, particularly on nights with a full moon. Moonlight may provide enough illumination for them to locate some prey items. This night feeding is likely opportunistic and much less frequent than daytime foraging.
Variation Between Individuals
As with many animals, there is individual variation among killdeer in their propensity for nocturnal activity. Younger birds and migrating individuals may be more inclined towards nighttime activity than breeding adults. A few specific birds, potentially influenced by factors like light pollution, may exhibit more regular nocturnal behavior than others.
Adaptability to Artificial Lighting
In areas where killdeer habitat overlaps with artificial lighting at night, some individuals may adapt their rhythms and utilize lit areas for evening feeding. This shows their adaptability but does not mean the species has fundamentally changed to become nocturnal.
Conclusion
In conclusion, killdeer are best described as a generally diurnal species based on most of their natural history and behavior patterns observed in the wild. The bulk of their activity related to vital functions like foraging, defending territories, mating, and rearing young happen in the daytime. However, killdeer exhibit some plasticity and may engage in occasional opportunistic nocturnal behaviors, especially during migration or under artificial lighting conditions. Overall, the killdeer is adapted as a diurnal species that is most active in daylight hours even though they may display some facultative nighttime activity.
Killdeer Nocturnal Activity Quick Facts
Evidence of Diurnal Activity Patterns | Observations of Possible Nocturnal Behavior |
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Killdeer Activity Levels Over 24 Hours
Time of Day | Killdeer Activity Level |
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Midnight to 4 AM | Very low |
4 AM to Sunrise | Increasing |
Sunrise to 10 AM | High |
10 AM to 2 PM | Moderate |
2 PM to Sunset | High |
Sunset to 10 PM | Decreasing |
10 PM to Midnight | Low |
This table summarizes the typical pattern of killdeer activity levels over a 24-hour period. Their diurnal nature is evidenced by high activity levels during daylight hours and far lower levels at night. The early morning and evening periods show transitional increases and decreases around sunrise and sunset.
Frequently Asked Questions
Why are killdeer rarely heard calling at night?
Killdeer do most of their loud calling during the day to defend nesting territory or when alarmed. Nighttime calling is rare because they cannot see well enough in the dark for visual territorial displays and have lower chances of detecting threats at night.
Do killdeer sleep at night?
Yes, killdeer spend most of the night sleeping or resting, conserving energy when they cannot actively forage. They become inactive at night with lowered body temperature and metabolism. Their main period of sleep occurs at night.
When are killdeer most vocal?
Killdeer vocalizations peak in the early morning at dawn and in the evening around dusk. This matches with times of activity transitions. Adults may also call actively when defending nests during daylight. Overall, their calling drops off significantly after dark.
Do killdeer ever migrate at night?
Most killdeer migration happens in daytime, but some nocturnal migratory flights have been detected around dusk, dawn, or on moonlit nights. Nocturnal migration is likely opportunistic and much less frequent than diurnal migration in this species.
Why don’t killdeer forage at night like some other shorebirds?
Many shorebirds use touch rather than sight when foraging in mudflats and can feed at night. But killdeer rely on vision to hunt insects and other prey in open, drier areas. Their visual foraging style is not well suited for nocturnal activity. Other plovers with similar diurnal feeding habits like piping plovers and semipalmated plovers also do not regularly feed at night.