Keeping track of bird populations can be difficult, especially on a small scale. It can be really hard to answer a single question about a noticeable decline in birds, but oftentimes we know, based on the season or larger factors at play, why birds may or may not be detected. My last column, answering “where are the birds?” is a good example of how every year, in the late summer, we know that statewide birds are seen less frequently, and for good reason. However, a separate string of inquiries this summer has me a little puzzled: where are the baby ducks?

Mallards, especially the ones in southern coastal Maine and urbanized areas, will start their first round of nesting in early April, and we typically see the first downy yellow chicks by mid-May. Things seemed normal this spring from my limited observations, and it was mostly in the second half of summer that I started getting inquiries about the lack of baby ducks, like from David and Janice who live on the Spurwink River and report seeing them every year – until now. Looking at data from Cornell’s eBird, an online database for people to submit bird observations, the frequency of mallards this year is right on par with the past five years, so on a statewide scale there were no obvious declines.

This winter, we’ll be able to pore through the breeding records that are being submitted to the Maine Bird Atlas, a project by the Maine Department of Inland Fisheries and Wildlife to document the breeding and wintering distribution of Maine’s birds, and perhaps tease out some of the annual fluctuations. But right now, it may be best for me to just be honest and say “I don’t know!” when asked what happened to those later ducklings.

I did do some research into mallard nesting to see if there are any obvious factors that could have been at play this year. An easy speculation to make is a connection to the drought conditions we experienced this summer. The idiom “happy as a duck in water” is quite accurate, with studies showing that mallards have more nesting attempts in wetter years, and that in eastern North America there is a positive correlation between annual recruitment – how many new individuals are added to the population – and late winter-spring precipitation levels. In May, about 40% of Maine was designated “abnormally dry” by the U.S. Drought Monitor, which increased to 70% in “moderate drought” by the end of June. These dry conditions may have been a factor.

Predation also comes to mind as a reason we wouldn’t see many babies. From snapping turtles to herons, and many mammals like foxes and raccoons, there are lots of predators that will go after a mallard’s nest or recently hatched young. Perhaps the recent years (everyone remember all those acorns, and the “squirrel-magedon” of 2018?) have allowed predator numbers to boom. In my literature review, I found a fascinating study from California that showed a positive correlation between small-rodent abundance and mallard nesting success. Apparently when voles are abundant, some of the mallard’s top nest predators will instead focus on rodents.

So I’ve got no clear answer yet. Keep submitting your sightings to eBird and the Maine Bird Atlas and with more data we can hopefully learn more about changes with our bird populations. In the meantime, it has been a fun question to ponder.

EVEN DOMESTIC CATS DO HARM

I had the pleasure of being on Maine Public’s Maine Calling show earlier this month to talk about birds and conservation. Naturally the unnatural topic of cats came up, since they are the number one anthropogenic cause of bird mortality, accounting for a conservative estimate of over 2.4 billion bird deaths per year in the U.S. One caller brought up a myth worth busting, which I’d like to do here – that the problem is just about feral cats. While they are the worst for wildlife, they are just part of the problem.

The famous (in conservation circles at least) report by Scott Loss, Tom Will, and Peter Marra (“The impact of free-ranging domestic cats on wildlife of the United States,” published in Nature Communications in 2013) that quantified the human activities that are directly leading to mortality in birds estimated that owned cats, allowed to free-range, accounted for 684 million bird deaths each year.

Yes, this is not as bad as the other 1.6-plus billion deaths being caused by feral cats (and remember, cats are non-native species brought to this continent by humans), but this number still towers over other anthropogenic causes. Building strikes (birds colliding with glass) account for 599 million, just shy of what owned cats contribute. Automobiles come in around 200 million, power lines at five million, and wind turbines at 573,000.

I hope that clears up any misconceptions. Any outdoor cat will follow its instincts to kill birds and other wildlife. Since we introduced them on the continent, we should have some responsibility to the animals that were here first. It’s also better for the health of our owned pets. Keep your cats indoors, or supervise their outdoor time. They’ll live long happy lives, safe from rodenticides or predators, like my two cats, Ruth Bader Kittensburg and Sonia Kittehmayor.

Do you have a nature question for Doug? Email questions to ask@maineaudubon.org and visit maineaudubon.org to learn more about bird walks, community science projects, and other programs about wildlife and habitat.

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