Waterfowl Declines in California

A flock of Mallards lifting off of a pond. Photo: U.S. Fish and Wildlife Service.

Each spring since 1948 staff from the California Department of Fish and Wildlife have conducted a survey of central and northeastern California to count the numbers of ducks and geese that are breeding in those areas. These counts are conducted by biologists flying in fixed-wing aircraft over the central and northern parts of California, and they form the basis of the California Breeding Waterfowl Survey. This long term data set is hugely powerful when scientists are looking at long term trends in populations and examining the effects of habitat loss, climate change, human population growth, pollution, and other factors.

Fixed-wing plane used during a breeding waterfowl survey over the Klamath River Basin. Photo: Keith Stein

The 2022 California Breeding Waterfowl Survey was just released and it’s not great. The total number of waterfowl breeding in California has declined 19% since 2019. All species were found to be in decline to some extent. Canada Goose were the least impacted with declines of 5% since 2019. Cinnamon Teal were hit the hardest with declines 54% since 2019. That means that there are only about half as many Cinnamon Teal breeding in California today as there were just four years ago! Mallard (the most common species of duck that breeds in California) and Gadwall were also hit hard with declines of 25% and 31%, respectively, since 2019.

These declines are in large part likely due to poor breeding habitat conditions. Ducks and geese need water to breed. The 2021-22 winter in California had below average precipitation across California, and the snow pack water content in California’s mountains is also below average. Such continued and serious drought conditions are resulting in less water for both natural and managed wetlands, and so to the poor breeding habitats and reducing waterfowl populations found in the survey.

Hopefully more water will fall in the state this coming winter. In the mean time, save water any way you can! The less water we all use, the more will remain in rivers, streams, reservoirs, etc. that can benefit the birds, fish, and other wildlife of California!

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Invasive Mute Swans

Mute Swans (Cygnus olor) are a species that is growing more and more numerous, and this is a problem.

Mute Swans are the “classic” swan from stories and art. They are large and showy and beautiful and these traits are exactly why they have been introduced to North America. Birds were brought from Europe in the 1800s and released in parks, gardens, etc. as ornamental additions (New York was the original release area). These birds have since reproduced and spread across the continent as far north as New Hampshire, as far south as Florida, and as far as west as California.

Adult male Mute Swan (Cygnus olor). Source: USFWS digital library.

They are becoming problematic for several reasons. One is that they are quite aggressive, and will chase and bite humans if that human trespasses on the swan’s territory. Another is that they consume quite a bit of food. They are big birds reaching up to 25 to 30 pounds, and that means they eat about eight pounds of aquatic vegetation every day. That is food which is then not available to native birds, and it disrupts habitat for native birds, mammals, fish, and other species. And a third reason is that the swans are directly aggressive to other species of bird driving them off nests, breaking eggs, and killing the chicks of other species, and so displacing those other species from areas where they would otherwise live. With habitats becoming ever smaller and more fragmented, this can mean the native species can be left with no where to go.

These problems have all contributed to Mute Swans being added to California’s restricted species list in 2008. This listing means the birds cannot be imported, transported, or possessed in the state without a permit. This has not completely prevented the swans from beginning to become established in California. Small populations can be found in Petaluma and the Suisun Marsh. I suggest that removing this species while the population is still small is the best course of action. There is every reason to suspect that the population will grow, and as it does so, the problems listed above will become more and more apparent. However, control will become more and more difficult.

One interesting thing about Mute Swans in North America is that they do not migrate very much. There are certainly some, relatively short, seasonal movements that occur in some parts of the continent, but not much. Certainly nothing compared to the long migrations that Mute Swans in Europe engage in. The evolution of this behavior in a novel environment illustrates how different geographic regions can cause a species to adapt and change. This behavioral evolution could then lead to the evolution of a new species, if it persists and becomes dramatic enough.

So, what can you do to help native birds and habitats, and prevent Mute Swans from taking over? If you spot a Mute Swan in California, contact the California Department of Fish and Wildlife – Invasive Species Program by sending an email to: invasives@wildlife.ca.gov or calling 886-440-9530. Together, we can act as citizen scientists to gather data that tracks where these birds are and how they move around. This data will help us all make the best and most informed decisions we can about this species.

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