Pelicans are a somewhat unusual sight in Denver, Colorado given that they are normally found in coastal areas. So why have these large seabirds taken up residence in the Mile High City? There are a few key reasons pelicans have been popping up in Denver lately.
Pelicans migrate through Colorado
Many pelican species, including the American White Pelican, are migratory birds. They breed in northern states and Canada during the summer months. Then they migrate south to warmer climates like the Gulf of Mexico coastline during the fall and winter. On their migration route, pelicans may stop to rest and feed on lakes and rivers throughout the western United States. This includes Colorado. While not a regular stopover point, Denver and Front Range lakes attract pelicans during migration season from August through November as a place to take a break before continuing their journey south.
Prominent sightings in Denver metro area
In the last few years, people have reported seeing sizeable flocks of pelicans hanging around bodies of water in and near Denver at times from late summer through early winter. Some of the more prominent pelican sightings in Denver include:
- Up to 300 pelicans spotted at Cherry Creek Reservoir in August 2021
- Around 500 American White Pelicans observed at Chatfield Reservoir south of Denver in October 2020
- Dozens of pelicans seen flying and resting at Sloans Lake in northwest Denver in September 2019
Pelicans stop to rest and refuel in Denver
Why would pelicans choose to stop in Denver when it’s not exactly on their typical migration route? Colorado’s Front Range provides abundant spots for the birds to land, rest and feed during their long journeys between their breeding and wintering grounds. Denver has several large reservoirs and lakes that make convenient stopover sites where pelicans can fish and build up energy before taking off again. The birds may stay for a few days or up to a couple weeks to rest and refuel.
Abundant food sources in Denver’s waters
One appealing factor is that Denver lakes and reservoirs harbor good supplies of fish, the pelicans’ main food source. Some of the fish species pelicans prey on include:
Fish Species | Locations Found |
---|---|
Carp | Cherry Creek Reservoir, Chatfield Reservoir |
Catfish | Chatfield Reservoir, Sloans Lake |
Trout | Chatfield Reservoir |
Crappie | Cherry Creek Reservoir |
This abundant food, combined with ample space to rest on the water, makes Denver an attractive temporary habitat for migrating pelicans to stop and refuel before moving on.
Pelicans may stay if food supplies remain
While most pelicans passing through Denver will stay for a short time before continuing their migration, some individuals may take up long-term residence if food supplies remain plentiful. Pelicans are opportunistic foragers and will stay in areas where they can find enough fish to sustain themselves. Lakes near urban areas often support higher fish populations than more remote lakes due to runoff and pollution. So reservoirs close to Denver may have greater food availability.
Sightings of resident pelican flocks
There have been sightings in recent years of flocks of 50+ pelicans apparently taking up seasonal or year-round residence in some Denver-area lakes rather than continuing migration. Examples include:
- A pod of around 70 pelicans stayed at Cherry Creek Reservoir from August through November 2021, much longer than the usual migratory stopover period.
- About 40 pelicans made Greeley’s Island Grove ponds their home in summer and fall 2020.
- Small flocks returned to Sloans Lake in 2019-2021, suggesting they may have taken up residency.
Pelican habitat range may be expanding
Another factor potentially contributing to increased pelican sightings in the Denver area is range expansion. The American White Pelican’s breeding grounds have expanded eastward in recent decades. They previously only bred west of the Continental Divide but now can be found breeding in lakes across the Midwest and northern Plains states.
Some research also indicates that the southern limit of the pelican’s winter range has shifted slightly northward in recent years. More pelicans may now be wintering in places like Texas, New Mexico, and southern Colorado that were previously just migration corridor stops. Denver is right on the edge of their expanded winter range.
Reasons for pelicans expanding range
Why would American White Pelicans be shifting their habitat range? A few possible explanations from ornithologists include:
- Climate change creating more favorable pelican breeding and wintering conditions farther inland and north
- Population rebound after the pesticide DDT was banned in the 1970s, allowing expansion into wider range
- Increased food availability in lakes, reservoirs, and aquaculture facilities across interior western states
These factors allow pelicans to take advantage of suitable habitat farther from the coasts. Denver may now lie within the expanded winter ranges of some pelican populations. This likely contributes to the regional uptick in sightings.
What impact do pelicans have on Denver’s ecosystem?
Pelicans are quite large birds, so an influx of hundreds stopping over along migration or taking up residence can have ecological impacts on Denver’s lakes and waterways. Experts are still studying how pelican presence may be influencing local fish numbers and water quality.
Potential positive impacts
- Pelicans help control populations of invasive fish like carp that disturb lake ecosystems if overpopulated.
- Fish remains and guano left by pelicans can fertilize lakes, improving water quality and food chains.
Potential negative impacts
- High concentrations of pelican guano may lead to excessive algae growth.
- Pelicans could deplete populations of desirable sport fish like trout if overfishing occurs.
- Large pelican flocks may compete for fish resources with other migratory birds.
Wildlife officials are studying these complex dynamics to understand if steps need to be taken to control pelican numbers and protect ecosystem balance. So far huge population crashes have not been reported, suggesting pelicans are not yet seriously distorting Denver’s lakes.
Conclusion
In summary, pelicans are appearing in the Denver region because it lies along their migratory route and provides prime spots to restock fish supplies as they travel to and from breeding areas. Lakes near Denver offer abundant food sources and lack major disturbances, making it attractive for migrating pelicans to stop. A small but increasing number are even taking up year-round residence as the pelican’s range expands. While pelicans passing through likely pose minimal ecological concern, officials plan to monitor their impacts if populations swell further. For now, Denver residents can enjoy the novel sight of these giant coastal birds gracing local waterways.