Nesting Habitat Destruction
House Finch on blackberry bramble. Photo by Catherine Keegan
In late June I received word that the large bramble thickets at the Noyo Headlands Park in Fort Bragg had been destroyed. A visit to the coastal trail confirmed that all bramble patches in the south end of the park had been mowed to the ground and shredded – along with an untold number of songbird nests, many with chicks. A phone call to the Fort Bragg Public Works Department confirmed that the City had destroyed those patches on the recommendation of the California Department of Toxic Substances Control (DTSC), after a local resident had reported seeing people eating berries in August of 2023.
Apparently, there was concern that the plants might be taking up toxins that had not been removed when the former lumber mill site was cleaned up before the park was developed. There is no evidence of this, and no risk assessment has been done to quantify the potential risk. DTSC chose to recommend the City of Fort Bragg either fence off the blackberry patches, put up signs warning people of the potential risk, or mow them down. The City chose the last option and scheduled the work at the worst possible time, right in the middle of nesting season, at a time when most eggs had hatched but the chicks were helpless. We had reports of adult birds circling the destroyed areas, searching for their lost nests and chicks.
We have no way of knowing how many nests were in those patches. California Quail love those big bramble thickets because they provide excellent cover, excluding most predators; even feral cats usually avoid them. The combination of cover and food supported an amazingly dense population of Song Sparrows. House Finches, White-crowned Sparrows, Orange-crowned Warblers, and hummingbirds were frequently seen in the brambles and likely all nested in them.
Brewer’s Sparrow. Photo by Catherine Keegan
City staff indicated that they never considered the birds when scheduling the work. One reason is that Himalayan Blackberry, the dominant species making up most of those thickets, is regarded as an invasive non-native weed with no habitat value. Introduced by Luther Burbank in the 1880s, it quickly spread across California and became widespread throughout the Pacific coast by the mid-twentieth century. That means it has been present in the environment for many generations of birds and other wildlife. That in turn means wildlife has adapted to its presence. To any songbird currently living in coastal California, Himalayan Blackberry is a natural part of the environment. The birds see excellent shelter – perhaps better than any native plant can provide – as well as abundant and diverse food resources. The berries are eaten directly by birds, and by many invertebrates that are in turn prey for other birds; the leaves are fodder for caterpillars, which attract many birds and are especially valuable during chick-rearing. If you have spent any time picking blackberries you probably noticed the abundant spiders, and those too are valuable sources of protein for chicks and for molting adults.
The good news is that the City of Fort Bragg did not treat the mowed crowns of the blackberry plants with herbicides and has no plans to do so. Himalayan Blackberry is notoriously resilient, and it is very likely that the thickets will grow back and re-establish the habitat within a few years – if they are not targeted for repeated destruction. It is my hope that we can help City staff find an alternative way to protect public health without destroying valuable habitat.
First published MCAS Black Oystercatcher September 2024
Song Sparrow on blackberry. Photo by Catherine Keegan.
