The black skimmer (Rynchops niger) is a tern-like seabird found along coastlines from North America to South America. Known for its unique bill, with a longer lower mandible than upper mandible, the black skimmer uses this specialized bill to “skim” the surface of the water with its lower bill partially submerged to catch small fish.
Unfortunately, the black skimmer faces a number of threats along its migratory flyways and in both its wintering and breeding grounds. Some major threats include:
Coastal development
Coastal development, including construction of homes, businesses, and infrastructure, destroys and degrades skimmer nesting and foraging habitat. As coastal areas become more developed, there are fewer places for skimmers to nest and feed.
Disturbance
Black skimmers are highly sensitive to human disturbance, especially at their breeding colonies. Activities like beach recreation, off-road vehicles, and pedestrians can cause adults to abandon their nests and chicks. Chicks and eggs left exposed are vulnerable to weather, predators, and death.
Pollution
Pollution, including oil spills, plastic debris, chemical contaminants, and wastewater discharge, can poison skimmer adults and chicks. Oil spills are especially detrimental, coating feathers and reducing insulation and waterproofing. Ingestion of plastics and contaminated fish can sicken or kill skimmers.
Predators
Predators including gulls, crows, raccoons, foxes, coyotes, and feral cats prey on skimmer eggs and chicks. Predation pressure on breeding colonies can be high without active management.
Climate change
Rising sea levels may inundate low-lying nesting sites. Increasingly severe storms threaten flooding of nests and chicks. Changes in water temperature and chemistry may impact prey fish populations and availability.
Fisheries interactions
Skimmers can get caught on fishing lines and hooks, become entangled in nets, and ingest fishing tackle. Fisheries activities may also reduce food availability for skimmers that rely on small bait fish.
Detailed Overview of Threats
Now let’s explore each of these major threats and how they impact black skimmer populations in more detail:
Coastal Development
The black skimmer relies on open, undisturbed beaches for nesting habitat. They prefer to nest just above the high tide line on wide, sandy beaches near optimal foraging grounds. Unfortunately, many prime nesting beaches have been lost or degraded due to rapid development along coastlines.
Construction of homes, hotels, restaurants, roads, marinas, and other infrastructure has eliminated or fragmented skimmer nesting habitat. For example, in 1996 it was estimated New Jersey had lost 80% of its coastal bird habitat in the preceding two decades. Development continues to whittle away critical habitat along migratory flyways.
Coastal development also threatens skimmer foraging areas. Skimmers rely on shallow, calm, clear waters to spot and catch small fish. But bulkheads, docks, bridges, and other structures alter water flow and clarity. Dredging degrades or destroys shallow flats used by foraging skimmers. Wastewater discharge introduces excess nutrients and contaminants.
As both nesting and feeding grounds shrink, the chances for successful skimmer breeding and survival decline. Nesting colonies become more crowded and may exceed capacity, lowering productivity. The loss of foraging areas means skimmers have to work harder and fly farther to find food for themselves and their chicks.
Disturbance
Black skimmers are highly sensitive to human activity and disturbance near their nesting colonies. The presence of people, vehicles, pets, or noise causes stress and interruption of critical nesting behaviors.
Adult skimmers may flush from their nests when disturbed, exposing the eggs or chicks to weather, temperature extremes, and predators. If people, vehicles, or pets enter the colony, eggs can get crushed and chicks killed by direct contact. Frightened chicks may stumble into the water where they are vulnerable to predators. There is also the risk adults may abandon the nesting site altogether if disturbance levels are severe.
Even minor passing disturbances can negatively impact the colony’s productivity and reproductive success. Studies have shown nesting skimmers that are flushed off their nests multiple times per day end up raising fewer chicks compared to undisrupted birds. One study in Texas found skimmer chicks were four times more likely to die in disturbed parts of a colony.
Some key disturbance issues include:
– Beach recreation – Activities like swimming, sunbathing, surfing, jogging, and watersports near skimmer colonies causes repeated flushing of adults from nests. Off-leash dogs often chase birds and destroy nests. Kite-flying is another problem.
– Fishing – Anglers walking through the colony, casting lines near nests, or cleaning fish at the site causes disturbance. Discarded monofilament line and tackle can entangle skimmers.
– Vehicles – Cars, ATVs, and other vehicles driving on the beach crush eggs and chicks and prevent adults from returning to attend the nests.
– Pedestrians – People walking through the colony cause skimmers to take flight. Unleashed dogs are also an issue. Even researchers monitoring the colony can cause disturbance if not careful.
– Predator control – While predator management helps reduce losses, actions like trap setting, shooting nuisance animals, and vehicle patrols can disturb skimmers.
– Aircraft – Low-flying planes or helicopters near the colony cause adults to leave their nests. Military training flights are a frequent problem at some sites.
The preferred management option is posting signs and symbolic fencing around the colony to create a protected zone free of human activity during breeding. Public education and outreach helps raise awareness. On-site monitors can gently deter disturbance events when needed. Closures of beaches and vehicle trails may be warranted to protect the most vulnerable sites.
Pollution
The black skimmer faces a variety of pollution threats across its range, both along migration routes and in its coastal habitat. Some key issues include:
Oil spills – Oil spills related to extraction, transportation, and storage of petroleum products can be catastrophic for skimmers and other beach-nesting birds. Even small amounts of oil reduce the waterproofing and insulation capacity of feathers. Ingestion from preening causes internal ailments.
Major spills like the 2010 Deepwater Horizon disaster in the Gulf of Mexico oiled hundreds of miles of shoreline and killed thousands of skimmers and other seabirds. Smaller spills from vessels and pipelines are a chronic problem along migratory routes and have damaged colonies.
Plastic pollution – Skimmers commonly ingest floating plastics they mistake for prey. Studies have found high levels (平均值)of plastics in skimmer chick boluses and regurgitations. Adults may feed plastics to chicks. Ingested plastics can obstruct or puncture the digestive tract, suppress appetite, or leach toxic chemicals.
Entanglement in fishing lines, strapping bands, bags, and other debris is also a significant problem. Trapped skimmers often die from injury, starvation, or predation.
Chemical contamination – Skimmers are vulnerable to bioaccumulation of heavy metals like mercury and organic contaminants like PCBs as they feed at the top of aquatic food chains. Legacy pesticides like DDT also remain at elevated levels in some areas.
Exposure can cause reproductive problems (e.g. eggshell thinning), immune dysfunction, deformities, and other effects. Toxins are passed from adults to chicks through the eggs.
Wastewater discharge – Release of insufficiently treated sewage introduces excess nutrients, chemicals, and pathogens into coastal habitat. This can promote algal blooms and alter prey composition, availability, and contamination levels. Fecal bacteria may directly infect chicks.
Trash dumping – Shoreline trash like bags, bottles, cans, and discarded fishing gear poses both a contamination risk and physical hazards to skimmers via ingestion and entanglement. Dumping is a chronic issue at some nesting sites.
Overall, proactive policies and regulation are needed to reduce pollution risks to vulnerable skimmer populations. Oil spill prevention and preparedness must improve. Public education can help reduce plastics and trash on beaches. Bans on harmful chemicals, enforcement of discharge permits, and wetland buffers all help protect skimmers from contaminants.
Predators
Black skimmers face heavy natural predation pressure at their breeding colonies. Common skimmer egg and chick predators include gulls, crows, ravens, coyotes, foxes, raccoons, feral cats, ghost crabs, and snakes. Predation is one of the main causes of nest failure.
While natural predation has always been an issue, human-related changes have exacerbated the problem in many areas. For example, predator populations may increase in size due to supplemental food sources from trash. Fragmentation of habitat creates dense nesting colonies that are magnets for predators. Disturbance by humans may flush adult skimmers off their nests, leaving the eggs and chicks easy prey. Artificial lighting may aid nocturnal predators.
In particular, large gull populations enabled by human food sources and management actions can lead to devastating effects. For example, colonies in New York and New Jersey suffered >90% losses of skimmer chicks to predatory gulls in multiple years.
Addressing problematic predation is challenging. Lethal control and live-trapping of key culprits like gulls, crows, foxes, and raccoons may help reduce losses but can be controversial. More common tactics include orienting colonies to reduce cover for predators, creating grid or radial fencing layouts with “gull-free” zones, and using spotlights to deter nocturnal predators. In some cases, constant monitoring along with hazing or removal of predators is needed to achieve nesting success.
Ultimately, multi-faceted strategies are required. Reducing natural and human food subsidies for dominant predators can help. Habitat management to disperse colonies can reduce attracting concentrated predators. Public education about not feeding wildlife or littering is also key. There are no easy solutions, but focused management and community involvement can reduce skimmer predation losses.
Climate Change
Black skimmers are threatened by various impacts linked to climate change. Some key issues along coastal nesting areas include:
– Sea level rise – Accelerating sea level rise driven by climate change will progressively inundate low-lying barrier island and beach habitat. Even a small rise can translate to large horizontal habitat loss. Nests flooded by high tides and storm surges will fail. Foraging may be impacted if tidal flats and shoals disappear.
– Increased storms – More frequent and intense coastal storms will threaten skimmer colonies with greater likelihood of overwash, flooding, sand loss, and even full breaching or island disappearance. Nests and chicks are vulnerable to washouts.
– Higher temperatures – Hotter temperatures may heat nests to lethal levels for eggs and chicks. Adults may spend more time away from nests trying to cool off. Overheating of foraging habitat may impact prey.
– Changes in precipitation – Altered rainfall patterns could increase or decrease river discharge into coastal waters. This affects salinity, nutrient inputs, sediment levels, water clarity, and prey populations for skimmers. More heavy rainfall can flood or erode nest sites.
– Shifting prey distributions – Rising sea temperatures, acidification, altered current patterns, and dissolved oxygen levels may cause fish prey to shift locations or decline. Less optimal foraging conditions would increase skimmer mortality.
– Increased toxic algae – Warmer waters are expected to increase harmful algal blooms that produce toxins dangerous to seabirds and their food sources. Die-offs have already occurred.
Addressing climate impacts will require reducing global carbon emissions coupled with local conservation actions. Habitat management like renourishment or elevating sites may sustain some nesting areas short-term. Making colony locations more resilient to floods and erosion is worthwhile but costly. Reducing other threats is critical so skimmer populations can better withstand climate shifts.
Fisheries Interactions
Black skimmers are vulnerable to adverse impacts from some types of commercial and recreational fisheries along the coasts where they feed and migrate. Some examples include:
– Bycatch – Skimmers can get caught on longlines, gillnets, trawls, and other commercial fishing gear. Drowning is common. Estimated hundreds to low thousands are killed annually in fisheries bycatch.
– Entanglement – Fishing line, nets, rope, and other gear can entangle skimmers and cause serious injury or mortality. Discarded tackle is a hazard at colony sites.
– Reduced prey – Overfishing may deplete food sources, especially critical forage fish populations. This forces skimmers to travel farther to find adequate food supplies.
– Ingestion of tackle – Skimmers can ingest fishing gear like hooks, sinkers, lures, and plastic baits while feeding. This may injure, poison, or starve birds if obstructing digestive tracts.
– Disturbance – Boating traffic and noise from fishing may displace skimmers from prime foraging and nesting locations.
– Contaminants – Chemicals like oil, fuel, and antifoulants used in fisheries may contaminate habitat and poison skimmers. Heavy metals accumulate in bird tissues.
Fishery management reforms can reduce risks to skimmers. Required bycatch mitigation measures, gear modifications to exclude seabirds, and spatial-temporal closures of fishing near colonies would help. Tackle cleanup at nesting beaches is also beneficial. Outreach to anglers and proper disposal of fishing gear helps prevent entanglement issues. Sustainable harvest levels for forage fish are also important for skimmer prey availability.
Population Status and Trends
What do we know about black skimmer population numbers and trends in light of these major threats?
The North American Breeding Bird Survey indicates skimmer numbers significantly declined at a rate of -2.2% per year from 1966 to 2015. The current population is estimated at about 78,000 breeding pairs.
Regional trends show the steepest declines in the Southeast Coast and Northern Atlantic Coast. Some state surveys indicate 75-90% drops in nesting pairs over several decades. For example, South Carolina had 30,000 pairs in 1977 but only about 3,500 pairs in 2012. However, a few regions like California have seen increases, likely reflecting distribution shifts.
The black skimmer is listed as Least Concern globally by the IUCN Red List due to its large range. But many experts believe numbers are declining more dramatically than surveys indicate, and that colony monitoring effort is insufficient to detect major losses along parts of the coastline.
More robust and up-to-date surveys focused on this species are critically needed to determine appropriate conservation status and recommend actions. Until better data are available, the precautionary principle would suggest assuming black skimmer populations are in significant decline due to the multiple threats described.
Recommended Conservation Actions
To stabilize and recover black skimmer populations, conservation practitioners suggest the following key approaches:
Habitat protection – Prioritize protection of remaining nesting colonies through acquisition, easements, or agreements. Prevent development and significant human disturbance at key sites.
Predator management – Use integrated, ethical control strategies to reduce excessive nest losses to dominant predators like gulls. Maintain natural ecosystem balances.
Reduce human disturbance – Minimize disruptive recreational activity and vehicle/boat traffic near colonies during critical breeding period through closures, rerouting access, ordinances, and public education.
Monitor and manage colonies – Support active programs to track, manage, and protect colonies, including stewardship groups. Take actions to maximize productivity.
Reduce pollution – Strengthen regulation, enforcement, and spill response to minimize pollution. Organize beach cleanups to remove marine debris.
Assess impacts of climate change and fisheries interactions – Research how climate pressures and fishery bycatch may impact populations to guide adaptation measures.
Coordinate regional and national efforts – Develop networks like the Atlantic Marine Bird Cooperative to share data, strategy, and policy needs across states and countries.
Engage the public – Partner with coastal communities on education and visitor programs. Increase awareness of skimmer conservation challenges and build support for solutions.
By implementing combinations of these and other science-based management recommendations, it is possible to bring black skimmers back from the brink and ensure healthy populations into the future. But action is urgently needed. Each nesting season lost is one fewer generation of skimmers to sustain this unique species.
Conclusion
The black skimmer faces serious threats across its coastal habitat from human disturbance, habitat loss, pollution, predators, climate change, and fisheries impacts. Regional population trends show concerning declines that require expanded monitoring and conservation action. However, strategic management focused on protecting breeding colonies, reducing mortality factors, and engaging local communities can successfully stabilize and restore black skimmer numbers. With proactive efforts now, it is possible to ensure skimmers continue gracefully skimming our coasts for generations to come.