Black skimmers (Rynchops niger) are unique seabirds that are found along the coasts of North America, South America, and the Caribbean. They are famous for their unusual bill shape, with the lower mandible longer than the upper one. This allows them to skim along the water’s surface with their lower bill partially submerged to catch small fish. Black skimmers nest in colonies, often with other seabirds like terns. Their nesting habits and sites are fascinating to learn about.
What kind of habitat do Black Skimmers nest in?
Black skimmers nest on open, sandy beaches and islands with little to no vegetation. They prefer islands and peninsulas separated from the mainland, which protects the colony from mainland predators. Ideal nesting habitat has a mixture of open sand for nesting and shallow water for foraging close by. Black skimmers also require a lack of human disturbance at their nesting colonies.
Some key features of good Black Skimmer nesting habitat include:
– Open, sandy beaches, sandbars, and islands with little vegetation
– Areas protected from mainland predators like foxes and raccoons
– Close proximity to shallow water fishing grounds
– Lack of human development and disturbance
– Spits, points, and shell rakes along barrier islands
– Dredge spoil islands
Nesting habitat availability limits Black Skimmer numbers in many areas. They nest in small colonies wherever suitable isolated, undisturbed habitat can be found.
What areas do Black Skimmers nest in?
The breeding range of Black Skimmers extends along the Atlantic, Gulf, and Pacific coasts of North America, throughout the Caribbean region, and down the east coast of South America.
Some key nesting areas include:
United States Atlantic Coast
– Virginia Barrier Islands
– Outer Banks of North Carolina
– Cape Romain, South Carolina
– Cape Islands of Georgia
– Florida Peninsula and Keys
United States Gulf Coast
– Chandeleur Islands, Louisiana
– Isles Dernieres, Louisiana
– Texas Coastal Islands
– Florida Gulf Coast
Mexico
– Baja Peninsula
– Coastal Islands
Caribbean Islands
– Bahamas
– Cuban Coastline
– Puerto Rico
– Leeward Islands
– Virgin Islands
Central and South America
– Yucatan Peninsula, Mexico
– Pacific Coast of Mexico
– Coastal Brazil
– Argentina Coastline
So in summary, important nesting areas are along sandy barrier island habitats of the Atlantic, Gulf, and Pacific coasts across the range of the species in the Americas.
What features make good nesting sites?
When choosing nest sites, Black Skimmers look for areas on open beaches with a mixture of sand and shell debris. Specific features that make good nesting sites include:
– Open sandy areas with little vegetation
– Sparsely scattered debris such as shells, driftwood, or pebbles
– Slightly elevated areas such as shell rakes or low dunes
– Sites protected by natural dunes or driftwood
– Areas with good drainage to avoid flooding
– Access to suitable nearby shallow water fishing grounds
– Lack of human disturbance
– Separation from mainland predators
Nesting spots usually provide some shelter from vegetation, driftwood, or other debris. Bare sandy areas with no cover are avoided. Nesting too far inland in dense vegetation is also avoided. Proximity to shallow fishing waters is important.
Ideal nest sites provide camouflage from predators, protection from weather, good drainage, and easy access to food sources. Human disturbance is always avoided. Finding sites with the right mix of these features drives the nest site selection process.
What is the nesting season?
The breeding season and nesting times for Black Skimmers vary across their range:
Southern USA and Mexico
– February to August
– Earlier in southernmost range
Mid-Atlantic and Northeast USA
– May to early September
– Peaks June to July
Florida
– April to August
– Varies by region within state
Caribbean
– Varies by specific island
– Usually April to August
The nesting season typically aligns with warmer temperatures and increased food availability. Further north, nesting starts later in spring and ends earlier in fall. Tropical areas have longer nesting seasons.
Nest initiation reaches a peak in May, June and July across most of the range. Some southern populations produce multiple broods in a season. Second nesting attempts may occur if the first fails.
What materials do they use to build nests?
Black Skimmer nests are simple scrapes in the sand. The birds use their bodies and feet to form shallow depressions in the substrate.
Nests are lined with any available debris in the immediate vicinity. This may include:
– Seashells and shell fragments
– Small pebbles or gravel
– Twigs, drifting feathers, or vegetation bits
– Sand
– Dried seaweed
The nest lining provides a little extra shelter and camouflage. But overall, Black Skimmer nests are very minimalist compared to many other birds. They do not bring in substantial materials from afar.
Pairs may re-use and maintain the same nest site across seasons and years. In familiar sites, old shell fragments often accumulate over time.
How do they choose nest sites?
Black Skimmers appear to choose nesting colony sites and individual nest spots opportunistically based on habitat availability each year.
Key factors guiding site choice include:
– Predator avoidance
– Human disturbance
– Access to food
– Drainage
– Shelter
Suitable habitat is limited, so birds settle wherever undisturbed nesting habitat is available in a given year.
Within a colony, pairs space themselves evenly throughout suitable areas. There is no evidence of strong nest site fidelity across years. Pairs will readily re-settle in new areas if disturbance forces relocation.
Nest spacing averages around 2 – 3 feet, which maintains social contact while minimizing competition. Nest density reaches about 2 nests per 100 square feet at peak breeding.
Do they nest alone or in colonies?
Black Skimmers are highly colonial nesters. They nest in groups ranging from a handful of pairs up to hundreds and even thousands of pairs.
Benefits of colonial nesting may include:
– Predator protection through group defense
– Social facilitation of breeding
– Efficient use of limited habitat
– Ability to locate rich food sources
The presence of other nesting seabirds like terns may help draw skimmers to suitable breeding sites. But they generally do not mix nests directly with other species.
Where large colonies exist, Black Skimmers nest in dense sub-groups or sub-colonies clustered in suitable areas of beach habitat. These aggregate into the larger colony.
How many eggs do they lay?
Black Skimmer clutches typically contain 3 to 5 eggs. The average is about 4 eggs.
Clutch size appears adapted to local ecological conditions. Smaller clutches of 2-3 eggs are typical in the southern reaches of their range. Further north, clutch size increases to 4-6 eggs.
Larger clutches may offset higher chick mortality in more seasonal environments. However, skimmers are limited in how many eggs they can successfully incubate. 5 eggs is highly typical for most regions.
Replacement clutches after nest failure may be smaller than initial attempts. Second nestings late in the year also tend to have fewer eggs.
Both males and females participate in incubating the eggs. They take turns shuffling the eggs beneath their dark black and white plumage.
How long is the incubation period?
Complete incubation from laying to hatching takes approximately 20 to 25 days.
Both sexes share equally in incubating the eggs. One mate will take over directly from the other with brief changeover periods. This constant changeover helps maintain proper egg temperatures.
In hot weather, skimmers may wet their belly feathers to provide cooling moisture to the eggs. In cold weather, the incubating bird keeps the eggs insulated beneath warm feathers.
Hatching is not perfectly synchronized due to slight variations in incubation start times. But under normal conditions, eggs in a clutch hatch within 1-3 days of each other.
Do both parents attend the nest?
Yes, Black Skimmers exhibit biparental care. Both the male and female partner remain with the nest and share equally in incubation and raising the young.
Typical roles are:
– Female – Main nighttime incubator
– Male – Main daytime incubator
– Both – Take turns foraging to provision chicks
Partners coordinate their behaviour to maximize efficiency in reproduction. Continuous sharing of duties allows each parent to spend time feeding.
When not incubating, adults aggressively defend the colony from predators. Paired mates remain monogamous at least for a breeding season if not longer.
How do the chicks hatch?
Hatching begins with the chick pecking a hole in the egg with its specialized egg-tooth. This tooth falls off soon after.
It can take 12-36 hours to fully emerge from the shell. Hatchlings are covered in patchy down and rely completely on their parents for survival.
Newly hatched Black Skimmers weigh only about 1 ounce (28 grams). But they grow and develop rapidly.
Parents immediately remove empty shells and egg fragments from the nest. This prevents attraction of predators.
Chicks hatch with their eyes open. They can vocalize from the moment they emerge to stimulate parental care instincts.
How do parents care for their young?
Both Black Skimmer parents are devoted caretakers of their offspring. They use a variety of strategies:
– **Shading** – Sitting over chicks to provide shade and reduce overheating.
– **Brooding** – Incubating chicks beneath their bodies for warmth.
– **Feeding** – Regurgitating fish directly into the mouths of begging chicks.
– **Guarding** – Aggressive defense of chicks and colony against predators.
– **Leading** – Coaxing mobile chicks towards the sea for swimming lessons and socialization.
– **Mobbing** – Dive-bombing predators in coordinated groups to drive them away.
Constant vigilance against predators is essential. Chicks shelter beneath adults when threats appear. Parents never abandon chicks to fate.
How fast do the chicks grow?
Black Skimmer chicks grow rapidly to attain flight capability in about 3-4 weeks. Key growth milestones include:
– **Days 1-5** – Remain at nest, downy plumage develops.
– **Days 6-10** – Begin wandering from nests while still unable to fly.
– **Days 15-25** – Acquire juvenile flight feathers and make short practice flights near colony.
– **Days 25-28** – Fledge completely and begin flying out to sea with parents.
– **4 Weeks** – Reach adult size but still perfect flying technique over subsequent months.
Rapid growth requires huge amounts of fish provided by both parents. Chicks beg and jostle for position during feedings. Growth rate determines survival chances.
What do parents feed the chicks?
Black Skimmer chicks are fed whole fish and aquatic invertebrates, like shrimp and crabs, regurgitated by parents.
Common prey includes:
– Small bait fish – anchovies, killifish, silversides, minnows
– Sand lance
– Mole crabs
– Shrimp and other small crustaceans
The size and type of prey reflect what’s available in the colony’s fishing habitat. Parents may travel substantial distances from colonies on long fishing trips to provision young.
Chicks are fed whenever parents return from foraging trips. Feedings become more frequent as chicks grow. Regurgitation allows transfer of whole undigested prey.
At what age do chicks fledge?
Black Skimmer chicks fledge at approximately 25 to 35 days of age. Fledging age depends on factors like:
– Food availability – Chicks may fledge faster in food-rich areas.
– Weather – Bad storms or cold weather can delay feather growth.
– Health – Parasites and disease can slow development.
– Predators – Need to flee dangerous colonies can accelerate fledging.
– Parents – Older, experienced parents tend to fledge chicks faster.
Fledging occurs when chicks make sustained flight out to sea, not just fluttering short distances. This is a critical survival milestone, allowing escape from predators.
What is the success rate of nests?
Nest and chick mortality is high. Only 25-30% of Black Skimmer eggs hatch successfully under natural conditions. Of hatched chicks, 50% or fewer survive to fledging.
Causes of nest failure include:
– Egg overheating – Due to parental neglect or hot weather.
– Egg chilling – Due to parental neglect or cold weather.
– Nest flooding – Due to storms, high tides, rain.
– Predation – Eggs eaten by predators.
– Weather events – Storms, hurricanes.
– Human disturbance – Causing abandonment.
– Infertility – From inbreeding or poor nutrition.
Surviving chicks still face hazards like starvation, predators, weather, and disease. High mortality leads to low annual productivity, especially in disturbed areas.
How many times do they nest per year?
Black Skimmers may attempt to raise one or two broods per breeding season. However, second nestings are only possible if the first is successful.
In the southernmost latitudes, skimmers may raise two broods. But further north, short breeding seasons limit them to a single nesting try.
Second nesting attempts typically occur 4-6 weeks after fledging the first brood. But rehabilitation from the high costs of breeding takes time, limiting multi-brooding.
After chick-rearing concludes in early fall, skimmer breeding behaviour ceases entirely. The pairs reunite on wintering grounds until the next spring breeding season.
Do both parents continue caring for fledglings?
Yes, after fledging both Black Skimmer parents continue tending to the juveniles and teaching them to fish.
Fledglings stay with their parents for several more weeks as they perfect flight and foraging skills. This family group structure allows further learning.
Key parental duties after fledging include:
– Leading juveniles to productive feeding areas
– Demonstrating fishing techniques
– Providing some supplemental feeds
– Letting young hitch rides to rest
– Guarding young at communal roosts
Gradually the young skimmers become independent. But they may remain with parents until departing the breeding grounds for migration.
Do Black Skimmers reuse the same nest sites?
Black Skimmers exhibit variable nest site fidelity between breeding attempts and across years. If conditions allow, they may reuse former sites, but fidelity is inconsistent.
Contributing factors include:
– Habitat availability – Existing colony sites may disappear.
– Predators – Heavy predation may deter reuse.
– Human disturbance – Favour undisturbed sites.
– Storm impacts – Erosion and flooding alters habitat suitability.
– Social attraction – Follow where other skimmers settle each year.
– Population density – When crowded, use marginal habitat.
– Mate fidelity – May return to previous site if mate remains same.
Nesting habitat is dynamic and unpredictable along coasts. Skimmers readily relocate nest sites adaptively as needed, rather than displaying strong fidelity to old sites.
Do the same pairs reunite in future years?
Some evidence indicates that Black Skimmer pairs may reunite on breeding areas over successive years. However, their mating system is not fully understood.
Contributing factors on mate fidelity include:
– Nesting success – Pairs who succeed may stay together.
– Winter flocking – May encounter previous mate.
– Site fidelity – Returning to same colony rejoins pairs.
– Seasonal timing – Synchronizing timing with previous mate.
However, skimmers likely exhibit a mixed mating strategy. Some instances of mate retention across years do occur, but periodic mate-switching also takes place.
Depending on circumstances, skimmers may either reunite with the previous mate or form a new pair bond when returning to breed. Their behavior balances stability with flexibility.
Do Skimmers nest with other species?
Black Skimmers are highly colonial and nest alongside other seabird species, especially terns. Common co-nesting species include:
– Least Terns
– Gull-billed Terns
– Royal Terns
– Sandwich Terns
– Common Terns
– Forster’s Terns
These species often occupy distinct but adjacent zones within a mixed colony. Some small intermixing may occur.
Benefits of multi-species nesting include:
– Joint anti-predator defense
– Wider detection of food resources
– Social facilitation of breeding
– Shared use of scarce habitat
Nesting associations provide protection and collective knowledge about local conditions. However, skimmers may also nest alone if no other seabirds settle in an area.
Conclusion
Black Skimmers have particular nesting habits adapted to their unusual ecology and coastal habitats. By understanding where, when and how they build nests and raise young, we gain critical insight into the conservation needs of these amazing birds. Protecting their sensitive beach habitats from disturbance is key so that successful reproduction can continue sustainably.
Some key points about Black Skimmer nesting include:
– They require undisturbed sandy beach habitats near productive shallow fishing waters.
– Nesting colonies can range from a few pairs up to thousands of pairs.
– Nests are shallow scrapes in open sandy areas with some scattered debris for lining.
– They are colonial but space nests evenly at 2-3 feet intervals to reduce competition.
– Clutch size averages around 4 eggs, with both parents sharing incubation duties.
– Chicks hatch after 20-25 days and grow rapidly, fledging in about 3-4 weeks.
– Parents use a variety of strategies to protect and feed the highly vulnerable chicks.
– Nest success is often low due to threats like weather, flooding, overheating and predators.
– Once chicks fledge, parents continue tending to them for several more weeks.
– Nest site fidelity between years is inconsistent, with skimmers readily relocating as habitat conditions dictate.
– Conservation of undisturbed nesting habitats is critical for Black Skimmer population health.
Understanding the Black Skimmer’s nest ecology provides a blueprint for effective conservation planning across their breeding range. Managing human recreational activities and mammalian predators in coastal zones during the nesting season is key. With proper habitat protections, these unique seabirds can continue thriving along our shorelines.