Dr. Marsha Sovada, wildlife research biologist for the USGS at the Northern Prairie Wildlife Research Center, spoke on Wednesday, March 18th at Weber State University. Click on ‘read more' below to find out more.
In all, there are only about 52 nesting locations known for American
White Pelicans (Pelecanus erythrorhynchos) in the world. About a half of the entire population breeds in just
four colonies located in the northern plains region (about 45,000
nests) of the United States. Another 10% -20% nest here in Utah on
Gunnison Island in the middle of Great Salt Lake. After studying
several northern plains colonies for a number of years during the
breeding season, Dr. Sovada and colleagues determined three major
threats to the population: disease, climatic conditions, and predator
Major Threats to White Pelicans in the Northern Plains
Disease, particularly west Nile virus outbreaks, seems to be the number one threat to northern plains colonies. For the past few years, major outbreaks have occurred every year around mid July. Although the virus does not seem to cause death in adult birds, it is responsible for killing approximately 80% of dying chicks in the population. Late season chick mortality was about 4% annually before west Nile arrived in the area. Currently mortality is up to about 25%, an affect that is likely to have long term affects on the entire population of American white pelicans. Dr. Sovada and colleagues are currently studying disease transmission and brainstorming methods to locally control the Culex mosquitoes that transmit West Nile.
Prolonged periods of cold, wet, rainy or windy weather in June or July after chicks have been left alone but when they do not yet have the ability to thermoregulate as well as adults can be detrimental to a population. Since birds seem to be arriving at nesting sites earlier each year over time, this could be more of a problem now and in the future than it has been in the past.
Finally, nesting pelicans are highly sensitive to the presence of predators. They will readily abandon their nest sites after disturbance. Coyotes are one of the biggest problems for nesting pelicans – even though they don’t directly kill a large proportion of the population, they cause enough disturbance, unlike the presence of other avian and mammalian predators, to lead to colony abandonment. In 2004, a subcolony of over 7,000 nests was completely abandoned at Chase Lake due to the disturbance caused by two pairs of coyotes later removed from the island. At Medicine Lake, two coyotes reached an island nesting site over ice during the winter and caused total abandonment of that site in 2007.
How do these threats relate to pelicans here in Utah?
An estimated 10,000 birds nest on Gunnison Island in the northwestern part of Great Salt Lake each spring. Given that the Culex mosquito vector of West Nile virus, while detected in Box Elder county, is not likely to be a problem on the remote, xeric Gunnison Island since mosquitoes need fresh water to breed. The fact that Gunnison Island is relatively mosquito free compared to other nesting areas farther north is all the more reason to do our best to continue to protect the pelicans on Gunnison Island from other threats such as predators. Gunnison Island may become an important refuge for breeding pelicans if problems with West Nile and harsh climate conditions continue to occur further north, potentially causing major decreases in the overall population.
The status of Gunnison Island is currently being threatened by an expansion proposed by Great Salt Lake Minerals. The expansion would include building dikes to form evaporation ponds within just a mile of Gunnison Island, likely making the island more easily accessible for coyotes and other predators. Pelicans sometimes return to an abandoned nesting site in subsequent years after a disruption event, but sometimes do not. If we want to ensure that American White Pelicans continue to nest here in Utah, we need to be proactive in our efforts to keep Gunnison Island as a predator-free nesting area for these birds.
Click here to read more about the expansion: GSLM Expansion,and make sure to check our website again in the future for updates as well as information about how to comment on the expansion proposal.
More background about American White Pelicans
American white pelicans nest on the ground. They lay 1-3 eggs per nest and both parents help to incubate the eggs for about 3 days before they hatch. For another 2 weeks, parents take turns feeding and caring for chicks. Pelicans are obligate brood-reducing species and typically only one chick survives due to sibling aggression. After 15-20 days, the adults abandon the nest site, only returning once a day to feed their chick. In the northern plains, pelicans return from wintering grounds along the gulf coast during March and begin almost immediately courtship behaviors that lead to nest building within just a few days. Densely populated subcolonies of synchronously breeding birds form on various islands and peninsulas. The peak of breeding is late April to early May.
For more information about Dr. Sovada’s research, click here: Sovada Research