ALBANY — So, where are all the birds this winter?
People are wondering because they say their feathered friends don’t seem to be frequenting their backyard bird feeding stations the way they did in winters past.
That seems to be a topic of conversation wherever birders flock this winter, whether it’s at the local coffee shop or such gathering spots for nature lovers as the Appalachian Mountain Club’s Highland Center, Green Mountain Conservation Group’s Blue Heron Bird Club or Tin Mountain Conservation Center in Albany.
According to birding experts interviewed this week, the disappearance of the birds may be due more to winter’s late arrival this winter and a warmer winter so far, allowing birds to find plenty of food in the forest rather than having to rely on bird feeders provided by humans.
As Will Broussard, outreach education coordinator for the Mt. Washington Observatory and a local birder, noted this week while showing off his bird-feeding station outside his North Conway apartment, “It’s been a late winter and a mild one so far, and it also was a big mast year in the forest, with many species producing bumper crops such as red spruce, white pine, white birch and yellow birch.”
Broussard said while he’s heard from people that there appears to be fewer birds at the feeders, “it is all anecdotal, and it is hard to base a scientific trend on anecdotes.
“I tell people to keep a list, recording what they see at their feeders as one of the many ways to document changes in songbird populations,” Broussard said.
Chris Lewey of Raven Interpretive Programs of Chatham concurs.
“When there is abundant wild food, the birds are not coming in for what humans offer,” said Lewey.
However, he, like many others, are voicing alarm at what they have read in a report released this past fall in the journal “Science” saying that the North American bird population of North America has dropped by 29 percent over the past 50 years.
According to the report, the net population decline in North America translates to about 3 billion birds since 1970. Yes that’s billion, with a “b.”
On Feb. 13, during a well-attended talk at Tin Mountain Conservation Center, Iain MacLeod, executive director of Squam Lakes Natural Science Center in Holderness and a master birder, took a closer look at long-term bird data in New Hampshire’s North Country. Alarmingly, he found similar declines.
“There are many questions,” the Scotland-raised MacLeod told the 60 or so attendees. “I don’t necessarily have solutions or answers to the question of why birds are declining. I can offer some thoughts, and I’d love to have your views, too, on what’s going on in any of your particular observations.”
Citing the “Science” report, which was titled, “Decline of the North American aviflauna,” MacLeod quoted the team of researchers — Kenneth V. Rosenberg, Adriaan M. Dokter, Peter K. Blancher, John R. Sauer, Adam C. Smith, Paul A. Smith, Jessica C. Stanton, Arvind Panjabi, Laura Jelft, Michael Parr and Peter P. Marra — as writing:
“A continent-wide weather radar network also reveals a similarly steep decline in biomass passage of migrating birds over a recent 10-year period. This loss of bird abundance signals an urgent need to address threats to avert future avifaunal collapse and associated loss of ecosystem integrity, function and services.”
“When I saw that,” MacLeod recounted, “I said, ‘Wow!’ It really jumped out.”
MacLeod started off with some basic bird population dynamics 101 to give the 3 billion number some context.
Some studies have suggested that there are 10 billion-20 billion birds in North America. Each spring, that population has the potential to breed and produce more baby birds.
“If we assume that there was a base population of 10 billion adult birds in 1970, those birds might have had the potential to replicate themselves four times over (an additional 40 billion eggs/birds — known as annual recruitment) every year,” MacLeod said.
“To see the sort of declines found in the report, annual mortality or impaired breeding potential is higher than recruitment.
Over 48 years, the base population might now have dropped to 7 billion adult birds with a breeding potential now reduced to 28 billion eggs/young.
“There are always winners and losers; some birds we know are increasing, and then most birds and in much larger numbers are declining. So they are talking about 3.2 billion lost,” MacLeod said.
“We’re talking a whole bunch of sparrows, wood warblers, Old World sparrows; nightjars, swifts, starlings, thrushes, larks, blackbirds, tyrant flycatchers and 28 other families,” he said.
MacLeod continued: “Some birds have increased over the last 40 or 50 years. Many raptors are more numerous now than they were 50 years ago. We’ve spent a lot of federal money and local money on bringing back bald eagle populations. Ospreys and turkeys are increasing, as are waterfowl. We all know there’s Canada geese everywhere ... So where we put resources, we have seen them do well.”
He said there have been some surprises — species that are bucking the trend, and scientists don’t know why.
“Gnatcatchers and red-eyed vireos are doing well. Red-eyed vireos were up 13.20 percent. We’re not sure exactly why. But generally we are seeing a decrease across the board over the last 40 to 50 years,” said MacLeod.
Of the red-eyed vireo’s robust presence, “The only way I can explain it is that they are gleaners — they eat a lot more caterpillars. Maybe there are more and more invasive caterpillars, coupled with warmer summers … they eat a lot of (the caterpillars), so maybe that’s the key to the vireo’s increase,” said MacLeod.
Breeding Bird Survey data show that in New Hampshire, 178 species were recorded on the 23 or so BBS routes surveyed annually from 1966-2018, and of those species, 53 percent show population declines; 42 percent are stable or show population increases; and 5 percent (nine species) were recorded so infrequently that no trends were calculable, MacLeod said.
“You might say, ‘Well, you know, only 53 percent are decreasing.’ But those 94 declining species represented 76 percent of the overall count from 1966 to ’75. But now they represent only 43 percent of the count from 2009-18. So, birds that were some of the most common species 50 years ago have declined the most,” he noted.
The American robin, for example, was the most common bird in the first 10 years of the survey from 1966-75, but its population numbers slipped 37.70 percent in the 2009-18 BBS, and the robin is now only the second-most common bird in New Hampshire.
The European starling showed a population drop of 78.70 percent and went from second place to 13th.
“That was a real surprise to me. But they’re often around grassland areas, and we’re losing grasslands, and they feed on bugs that might be getting hit hard by pesticides,” said MacLeod.
The song sparrow, he reported, has dropped 33.13 percent, going from fifth to ninth place; the red-winged blackbird was fourth and is now 10th, down 51.02 percent; the wood thrush — known for its beautiful forest song — dropped from sixth place to 38th, down 84.50 percent; the common yellowthroat remains in seventh place but dropped 20.80 percent; the barn swallow was eighth but dropped 79.39 percent to 32nd place; the white-throated sparrow (“One of those beautiful iconic songs of the North Country — vanishing,” MacLeod said, eliciting a knowing groan from the audience of birders), is down 71.22 percent, dropping from ninth place to 26th; and the tree swallow declined 67.38 percent from 10th place to 24th on the list.
“The swallows are both grassland species, and their habitat is disappearing. That may offer a clue behind their decline,” said MacLeod.
The current top 10?
As mentioned, topping the list is the red-eyed vireo, followed by the American robin. The American crow jumped 83.5 percent from 16th to third; the chipping sparrow was 21st and is now up 87 percent to fourth place; the ovenbird that was 14th has increased 25 percent and is now fifth; the black-capped chickadee that was 20th has jumped almost 63 percent and is now sixth; the common yellowthroat as noted has declined almost 21 percent but is still in seventh; the cedar waxwing has gone from 29th to eighth place, nearly doubling to 99 percent; the song sparrow was fifth but dropped 33 percent to ninth; and the red-winged blackbird was fourth but dropped 51 percent to 10th place.
The purple finch, the New Hampshire state bird, has shown a 60 percent decline. The Baltimore oriole? “Sorry; they’re declining,” MacLeod said.
Species that are increasing include pileated woodpeckers, the common raven, the wild turkey and Cooper’s hawks.
He said there are “two big elephants” in the room when it comes to the possible reasons for the overall decline in the bird population.
“The first is the insect apocalypse: recent studies suggest we have lost perhaps 50 percent of all insects globally since 1970,” said MacLeod.
And the other major factor, MacLeod asserted, is climate change.
“Basically it’s not getting as cold in the winter and it’s getting warmer in the summer,” said Macleod. “Ice out on Lake Winnipesaukee has been increasingly earlier by two weeks over the last 100 years. We’re getting more rain. The weather is changing. The range of certain plant species is changing. Certain trees are moving northward and the birds have to follow the habitat. Forest pests and pathogens have changed. These changes are happening faster than birds can adapt to.”
He said birds wintering in the tropics are triggered to head north by the changes in the length of daylight. But when they fly north to our neck of the woods, if insects are hatching earlier due to the warmer weather, when the birds arrive on time they may find that the food supply has been diminished by the birds who arrived earlier.
He outlined some other causal factors that might account for that 40 billion annual mortality/lost breeding potential number.
According to MacLeod, there are studies showing that there are 86 million pet cats in North America and an additional 50 million feral cats — studies suggest that approximately 2 billion birds per year are killed by cats in North America. He said perhaps 600 million birds are killed every year through window strikes.
He added that some studies have suggested that increasing human population and more urban sprawl lead to a loss of habitat.
Vehicle collisions are another factor, with over 200 million birds killed every year.
He said that he took a look at neighboring state data concerning declines and was surprised to find that the declines are much more significant in Maine and Vermont than in more populous areas such as Massachusetts and Connecticut.
“So,” said MacLeod, “that says that the fact that there’s a lot of people there and urban sprawl, backyards, cats and cars, that’s not really what’s causing the disparity.”
He also said there are 50,000 wind turbines in the United States but fewer than a half-million birds are killed from turbine collisions each year.
He also said there are 300,000 communication towers in the nation, which account for the loss of up to 7 million birds — but again, when it comes to New England, the majority of the towers and wind turbines are in more populous states such as Massachusett. So, said MacLeod, “I don’t think that’s the smoking gun.”
He talked of approximately 3 million raptors that kill perhaps 2.5 billion songbirds a year. Add all of those factors up, MacLeod said, and there might still be 35 billion fewer birds that cannot be explained away by the turbines, towers, cats, collisions and raptor kills.
Leading back to the two big elephants in the room: insecticides and climate change.
MacLeod didn’t have all the answers for the decline but did offer ways that humans can help make a difference — and advocated that all contact their legislative leaders to press for action on climate change.
They can also continue to do things such as put out bird feeders, keep their cats indoors, refrain from using insecticides, grow native plants and let their yards grass grow uncut which attract native insects which attract native birds. “I know it’s not a very uplifting program, because the story with our bird populations is not that great,” MacLeod said.
Lewey said there are things people can do.
“People can choose bird-friendly coffee … They need to pay attention to pesticides here and in South America,” said Lewey, adding, “We need to influence the legislation end of things and not let the dollars side of things sacrifice the environment ... Federal laws are being overwritten to allow for big business to destroy nesting habitat. It is not a good situation.”
For more about the study or local birding programs, go to the Squam Lakes Science Center website at nhnature.org; or to sciencemag.org/news/2019/09/three-billion-north-american-birds; nhaudubon.org; ravenprograms.com; or tinmountain.org.