Biologist Kathy Molina was making one of her regular surveys of the Salton Sea National Wildlife Refuge on a recent Friday. Molina keeps tabs on several species of rare sea birds that use the Salton Sea as a nesting spot.
Some birds, such as the gull-billed terns, have been struggling recently to keep their numbers up in the face of increased competition for nesting spots from larger birds.
“It’s looking a lot worse for the smaller species. Because they’re smaller, the bigger guys just kind of push them aside, and so they’re moving. They’re constantly being challenged for a lot of competition for nest space,” Molina said.
This year, that nest space has been further poached by thousands of adult California brown pelicans that are showing up months earlier than normal to roost in spots inland from their normal nesting areas.
Dan Cooper, a biologist who monitors birds at Malibu Lagoon, said he first noticed the birds’ strange schedule in mid-April.
“I was just sort of flabbergasted at seeing 3,500 brown pelicans resting in Malibu Lagoon,” Cooper said. “I checked my notes, and I have numbers in the hundreds, but I’ve never seen anything like that.”
Failed nesting season
While the pelicans regularly use the Salton Sea each year, Molina said it’s usually not until after the other birds’ nesting seasons.
On Friday, the pelicans ringed small islands, both natural and man-made, in freshwater ponds along the sea’s edge. They stretched and preened, almost as though they were on vacation. Molina said she’s seen thousands of the large birds each time she’s come recently.
“The absolute numbers are not shocking. It’s just the timing. They’re early, and when they’re early like this, that’s when they impact our nesting birds,” Molina said.
The pelicans themselves aren’t nesting or rearing young. They’re roosting — essentially hanging out in spots near food sources.
Scientists say that a shift in the locations of their fish food sources has made it difficult for the birds to get enough nutrition to raise young. As a result, the majority of brown pelicans have given up the attempt for the year.
For the past 46 years, Dan Anderson, a professor emeritus at the University of California at Davis, has visited the Baja Peninsula, where 80-90 percent of California brown pelicans are born. This year, he said that he estimates pelicans have reared less than one percent of the young they normally would.
“It’s been almost a nearly complete failure to breed, which is quite unusual actually,” Anderson said. “At one island that we study, Isla Salvatierra, which would normally have 8,000-10,000 young, only had like 20 young.”
A case for El Niño?
Scientists say a lack of fish food sources, such as sardines and anchovies, has caused the widespread nesting failure. That change of availability may be an early indicator of an El Niño climate event.
El Niño events bring warmer water to the Eastern Pacific Ocean, which can in turn cause rainier winters for California. Scientists have been closely monitoring ocean temperatures and have predicted that an El Niño event is 78 percent likely to occur next year.
But the natural world may also be giving an indication that an El Niño is coming.
In 1982, Ralph Schreiber, a curator at the Natural History Museum of Los Angeles County, went to study birds on Christmas Island in the Pacific Ocean, expecting to see millions of breeding pairs. Instead, practically all of them were gone. Schreiber realized that warmer waters had disrupted fish populations around the globe.
“This was the first time that a major El Niño event could be directly tied to these massive breeding failures,” said Kimball Garrett, ornithology collections manager at the Natural History Museum. “It’s become clear that this can happen in many areas and not just that little narrow area along the equator.”
Anderson said that the pelicans’ behavior seems to be indicating that an El Niño’s effects may be having an impact even earlier than anticipated.
“The El Niño hasn’t been predicted to set in until later this year, but apparently it’s earlier, or the birds are somehow sensing that things aren’t so good,” Anderson said.
Even if one does come, however, it doesn’t guarantee an end to the current drought.
“While that’s one set of possibilities, it could also just turn right around, and we could have another year or more of drought,” said Garrett. “We just don’t know.”
Possible population threat?
The brown pelican was only removed from the endangered species list within the past five years. The population had taken a large nosedive after DDT contamination caused the birds to lay thin-shelled eggs, which cracked prematurely.
Despite the brown pelican’s nascent recovery status, scientists said that they aren’t concerned this year’s nesting failures will overly damage the population.
“They’re very long lived for birds. They’re going to live to breed for even decades, and a single-season failure is almost meaningless to the population,” Garrett said. “Just a couple years of success can really turn things around when you consider that a bird in essence only needs to replace itself in its lifetime for a population to be stable.”
Dan Anderson said that it’s not out of the ordinary for El Niño to affect breeding.
“El Niño is a regular phenomenon. About 35-45 percent of the time, the birds are under El Niño conditions. They generally don’t breed well during El Niños,” Anderson said. “However, as soon as conditions return, they bounce right back.”
That said, he said that if it is an El Niño event causing the breeding failures, it'll likely cause a second subsequent year of failures as well.
"It may be a two-year event for them. Too many two-year events do cause population problems. Our models show that if you have too many, they start to take a bite out of the population," Anderson said.
Back at the Salton Sea, it was clear to Kathy Molina that regardless of whether a wet El Niño is on the way, the impact on pelicans is having ripple effects. At one pond, where hundreds of pelicans were dominating island property, Molina described the sound as "a colony on the wane."
"This should be just a cacophony of Caspian terns, and gull-billed terns and skimmers. They should all be coming in with food, feeding their chicks, vocalizing to their mates or their chicks," Molina said. "This is really quiet."