Many species make up part of the food web for Pelicanus, including the fishes mentioned above (Striped Mullet, anchovies, menhaden, etc) but also the food sources that those fish consume including the various smaller fishes, planktons, and sea kelps such as Sugar Wrack and Sea Palms that provide up to 90% of the primary productivity for intertidal ecosystems.
Pelicanus has no known predators though in areas around Tijuana, Mexico are known for places where humans gather Pelicanus eggs for consumption, though that is illegal in the United States for many reasons, not limited to its current status as Endangered or Threatened depending on the jurisdiction and region Pelicanus inhabits around the country.
The historical range of Pelicanus in the United States includes the Pacific and southeastern coastal areas, as well as Central and South America, occasionally reaching up to Vancouver Island. They were wiped out of Louisiana in the early 1970s due to chemical pollutants including DDT and other pesticide residues that disrupted solid eggshell production. At the peak of their decline in California in 1971 only one bird hatched, but after the passage of a ban on DDT use by the EPA in 1972, breeding success improved greatly to hatched numbers reaching 6500 and more in the mid-80s. Currently, Pelicanus continues to inhabit much of its historic range and can be seen expanding this range inland here and there but not for breeding.
This species is unique in that it is one of the largest seabirds and certainly the largest (and only Brown) of the 7 species of Pelicanus worldwide. It’s habitat, which is mostly ocean waters and breeding sites need to be restored to more pristine conditions free of pesticide and heavy metal residues coming from inland runoff and sewage outlets as well as development along estuaries and coastlines, to ensure long term success of the species.
Pelicanus is a migratory seabird so it moves around to many different regions that have both easily maintained habitats and delicate habitats. Some regions it feeds from contain organisms that are sensitive to warming water temperatures and a important source of food could be lost if climate change dramatically alters the temperatures of some of these regions. In addition, Pelicanus needs areas close to the ocean to breed and so tree tops and bushes in coastal scrub areas need to be designated wild and scenic or wildlife preserve lands so they can safely mate and fledge their offspring in these regions. Pelicanus is a colonizing bird that often nests within a wings distance of each other and there for to support a population of 4,000 or more breeding pairs would require large tracts of undeveloped or seldom used space at least during their breeding season of late summer.
The most important aspect of habitat restoration for Pelicanus occidentalis is the necessity to reduce our toxic chemical and heavy metal use in industry manufacturing, processing, agriculture, and sewage treatment as these elements are the most destructive to their environment and their effluent and pollutants are systemic through the food chain. While some measures have been proposed such as the banning of various chemicals like DDT, and moving sewage outlets farther out to sea, problems still arise with the use of other chemicals not yet banned, the use of chemicals that contain trace amounts of DDT which are still used, legal use of DDT and similar chemicals in Mexico, and illegal use here in the US. Concentrations are found in many species still today that are above the National Academy of Sciences safe limits, and while moving sewage outlets farther away from intertidal communities and areas of high biodiversity, the problem is not solved or mitigated just moved to another region that is now in danger of further human disruption and continued exploitation without regards to ecological needs and balance.