While a variety of pressures make survival difficult for these birds, four factors are the most significant within Recovery Unit 2 (Del Norte, Humboldt and Mendocino Counties).
Predators are the most significant factor affecting reproductive success of snowy plovers. Small mammals, such as fox and raccoon, and birds, particularly the common raven, prey on the eggs and chicks of snowy plovers. Occasionally, birds of prey also take adults decreasing the entire population.
Loss and degradation of breeding habitat is another factor affecting snowy plovers. They prefer open, sandy areas with sparse and low lying vegetation for nesting. Due in large part to the spread of introduced plant species, principally European beach grass, the amount of suitable nesting areas has diminished.
Human activities including encounters with people, dogs and vehicles as well as trash left behind can threaten the breeding success of snowy plovers. Energy is very important to this small bird. Every time humans, dogs, or other predators cause the birds to take flight or run away, they lose precious energy that is needed to maintain their nests. Just the presence of people and dogs in close proximity can cause adults to temporarily leave nests, which increases the chance of a predator finding the eggs, sand blowing over and covering the nest, or the eggs getting cold. Litter and food scraps left behind attract predators such as ravens and raccoons which could increase predation of eggs and chicks.
Inclement weather such as winter storms, river flooding, high tides and strong winds can be detrimental to both breeding success and winter survival. Nests can be washed out during river flooding or covered by sand during strong winds. In the winter time, snowy plovers need all of their energy to stay warm and survive through extreme weather conditions.
Frequently Asked Questions
Q: I see hundreds of snowy plovers running around on the waveslope why are they listed as threatened?
A: If you see hundreds, they are not snowy plovers. They are likely sanderlings, which look similar and are often mistaken for them. If the birds you see run in and out with the waves looking for food, they are not likely snowy plovers.
Q: What do snowy plovers eat?
A: Snowy plovers feed on invertebrates, such as beach hoppers, in piles of seaweed and debris along the high tide line. Snowy plovers glean insects from the surface versus probing under the sand like many other shorebirds.
Q: Why are there roped off areas on local beaches every summer?
A: This “symbolic” fencing helps alert beachgoers to the presence of snowy plovers and encourages them to avoid potential nesting and rearing habitat during breeding season (March-September). At Little River State Beach, some fencing was put up to protect habitat restoration areas and the native plants.
Q: Are the conservation efforts working?
A: Recovery efforts throughout the western snowy plover range have proved effective at boosting populations. In Recovery Unit 2 (Del Norte, Humboldt and Mendocino Counties), active protection of plovers began in 2000. This may seem like a long time, but it takes many, many years for populations of threatened and endangered species to rebound. There are many factors that influence population size, some of which we have no control over. For instance, the winter of 2005 and 2006 was particularly cold and wet, and resulted in a drop in the adult population. Since then the population has been increasing.
Q: How does European beachgrass affect snowy plover breeding success?
A: European beachgrass, an exotic invasive, creates an impenetrable vegetative barrier for chicks between foraging and potential nesting habitats. Recent studies show European beachgrass communities have reduced invertebrate densities compared to native vegetation. Snowy plovers feed on invertebrates and tend to nest in open sandy areas with sparse or low lying vegetation. Native dune vegetation is more cryptic, low lying and provides good visibility for spotting approaching threats.