The brown pelican (Pelecanus occidentalis) is a large seabird found on the coasts of North and South America. They are known for their large throat pouches used for catching fish, their primary prey. Brown pelicans are opportunistic feeders and their diet consists mainly of fish found in warm shallow waters. Some key facts about the brown pelican’s diet and foraging habits:
Preferred Prey
– Small surface-schooling fish are the brown pelican’s preferred prey, including anchovies, herring, mullet, minnows, and sardines. They need to eat around 0.5-1.0 kg of fish per day.
– Their diet varies based on location and fish availability. On the Pacific Coast they eat primarily anchovies, herring and sardines. In the Gulf Coast their diet consists more of menhaden, mullet, sheepshead and grunts.
– Brown pelicans will also opportunistically feed on crustaceans like shrimp and small lobsters.
Hunting and Feeding
– Brown pelicans hunt by diving head first into the water to catch fish in their throat pouch. They can submerge up to 1–2 meters deep to catch prey.
– Upon surfacing, they drain the water from their pouch before swallowing the fish whole. The pouch can hold up to 3 gallons of water and fish.
– They primarily feed by plunge diving, but will also surface feed by dipping and scooping fish out of the water.
– Brown pelicans may also steal food from other seabirds or scavenge dead fish found floating on the surface.
Adaptations for Fish Hunting
– The brown pelican has a number of physical adaptations to help it catch fish:
– Large webbed feet and toes help propel and maneuver underwater.
– A large gular pouch on their throat is stretchy and can balloon out to capture large amounts of prey.
– Sharp hook at the end of the beak that can snag slippery fish.
– Excellent eyesight to spot fish swirling near the surface.
– Lightweight skeleton and minimal feather covering to decrease buoyancy while diving.
– Superb swimming capabilities, using partially opened wings for agile steering underwater.
Diet Composition and Variation
Several studies have analyzed the diet composition of brown pelicans across different regions to understand geographic, seasonal and age-related variations:
Pacific Coast
A study examining regurgitated food from pelican chicks in southern California found:
Prey Species | Frequency of Occurrence |
---|---|
Northern anchovy | 87.2% |
Pacific sardine | 44.8% |
Pacific mackerel | 41.4% |
Jack mackerel | 24.1% |
This shows anchovies and sardines comprise the majority of the diet on the California coast.
Gulf Coast
A study in Texas found the most common prey items to be:
Prey Species | Frequency of Occurrence |
---|---|
Gulf menhaden | 22.7% |
Pinfish | 18.3% |
Spot | 13.4% |
Atlantic croaker | 9.2% |
The diet consisted primarily of small schooling forage fish like menhaden and pinfish. This demonstrates geographic differences in prey availability.
Seasonal Variation
– Diet composition changes seasonally with fish migration and spawning patterns.
– There is greater diet diversity in winter and spring. In summer and fall, anchovies and sardines comprise up to 90% of the diet.
– Adult pelicans also feed on larger fish like mackerel, corbina and surfperch during the summer months when juveniles are abundant.
Age-Related Differences
– Adult pelicans generally take larger fish than juveniles. Average prey size correlates to pouch size and diving capability.
– One study found the mean size of prey taken by adults was 60.6 g compared to 8.8 g for juveniles.
– Adults also feed further offshore than juvenile brown pelicans.
Impact on Local Food Webs
As keen fish-hunting specialists, brown pelicans can have a significant impact on local marine food webs. Some key effects include:
– Brown pelicans are estimated to consume between 6-12% of the available fish biomass in areas where they feed. Their high consumption is believed to exert top-down control on fish populations, particularly small schooling species like anchovy, menhaden and herring.
– Declines in pelican populations from environmental threats can release predation pressure on prey fish stocks. However, the impacts are complex due to other fish predator-prey interactions.
– Brown pelicans may compete with commercial fisheries for certain prey fish populations. There are concerns over potential competition with fisheries targeting anchovy and herring stocks.
– As opportunistic foragers, brown pelicans are able to switch prey when a preferred fish stock declines. This adaptability helps buffer their populations from over-exploiting any single prey species.
– Brown pelicans are an important sentinel species reflecting local fish abundance and health. Changes in diet, body condition and breeding success indicate fluctuations in prey fish populations.
Conservation and Threats to Prey
Several factors can threaten the brown pelican’s food supply:
– Overfishing of key prey like anchovy, sardines and menhaden stocks have caused periodic crashes in brown pelican populations that rely on these fish.
– Habitat destruction in coastal wetlands eliminates crucial nursery grounds for many pelican prey fish species.
– Oil spills directly kill prey fish and contaminate pelican’s feathers causing hypothermia and starvation.
– Pollution and algal blooms can diminish water quality and available prey.
– Climate change will alter fish stock productivity and availability.
Protecting adequate prey fish populations and coastal wetland habitats is vital for sustaining healthy brown pelican numbers over the long-term. While adaptable and opportunistic, the brown pelican depends on sufficient fish stocks within reach of its specialized plunge-diving hunting strategy.
Conclusions
In summary, the brown pelican is a piscivorous specialist that feeds primarily on small schooling fish like anchovies, herring, menhaden and sardines. Their diet varies geographically and seasonally based on local prey availability. Brown pelicans are prolific predators that can significantly control prey fish populations on which they rely. Ensuring healthy fish stocks and wetland habitat is crucial for maintaining brown pelican numbers. As sentinels of coastal ecosystem health, conservation of the brown pelican goes hand in hand with protecting marine food webs.