From May to the end of July, it seemed to slow down, and young birds from the mid-Atlantic to the Midwest became sick and died with strange symptoms. Scientists are puzzled by mass deaths. A few months later, they still don’t know what killed these birds. Suspects include pathogens that the victim may be infected by eating X-type cicadas and environmental toxins that young birds are particularly susceptible to infection.Brian Evans, an ornithologist at the Smithsonian’s National Zoo and Conservation Biology Institute in Washington, D.C., led an exploit Community science Learn more about the scope of the incident and narrow down the possible causes.
Scientific american Talked to Evans about the efforts to solve this persistent mystery, the influence of community scientists, and what the public can do to help.
[An edited transcript of the interview follows.]
When did you first know that these songbirds died?
It first caught my attention in early to mid-May. At first, I didn’t believe it. I know that the mortality rate for fledglings is generally very high. Therefore, frankly speaking, as an ornithologist, I am not so surprised to hear that a group of people have observed many dead and dying chicks.At that time, there were about five birds in my backyard that basically fell from the sky. I blamed the crows because there is an incredible population of crows near me. [in Takoma Park, Md.].
It wasn’t until late May that my views on this incident began to change.One of my neighbors observed a bird on the street in front of the yard, and it was still alive — all the birds I encountered at the time were dead — and described its eyes as really swollen, and could not respond to her and just [seeming] Generally confused. Its head is shaking.In my opinion, this seems to be a strange set of symptoms to share: we see a lot of swollen eyes in birds, especially house sparrows and sparrows, which are infected with a kind of Mycoplasma gallisepticum. But the symptoms she described don’t sound like [those] Caused by mycoplasma.
At that moment, I went from really doubting to beginning to doubt myself. After half an hour, I received a text message from the on-site technician. [Smithsonian] There was a photo of an affected bird in the migratory bird center. A neighbor called me and told me he had a sick bird on the road.
He and I went to City Wildlife, a rehabilitation organization that played a vital role in publicizing the incident and contacting all parties. When I went there, they told me that from their point of view, it was a serious incident and that they were at a loss for the upcoming death toll.
What are the symptoms of this condition and which birds will be affected?
Ophthalmological symptoms may be unexpected swelling of the eyes, which stick out a little bit from the head. They can be crusty eyes; they can be blind. Nervous system symptoms may be head shaking, inability to stand, and involuntary muscle cramps in general. [They] It may be depression or drowsiness. When you observe one of the birds with neurological symptoms, it is quite obvious because they just don’t respond.A video has been submitted [via a form that the Smithsonian National Zoo and Conservation Biology Institute set up] The bird shook his head slowly, barely able to stand up, and fell to the side. I think the most striking thing in this incident is the strange behavior.
As far as we know, [of those] Affected, maybe 90% [are] juvenile. It can be tricky to distinguish juvenile fish from adult fish, but in the early stages, they look very different, especially in terms of feathers, and when they are young, they have large fleshy mouths around the corners of their mouths.
Once you realize that these are not the ordinary deaths among teenagers you expect, what have you done?
The first thing we did was to start coordinating with the rehabilitation organization City Wildlife. We send emails back and forth and try to understand: what do we know?This is just now [Washington], DC, or in another state? How many birds are affected? Are we the worst?
We collected samples with neuro/ophthalmological symptoms related to the event and conducted internal tests on them through our Conservation Genomics Center to detect everything from viruses to bacteria to fungal infections.
Another role I play is to contact all the rehabilitation institutions I can find that have specimens of birds that have died from other causes-so they died because they hit a window or because a cat killed them. Finally, we are testing truly healthy specimens: we are going to enter the environment, we are banding the birds and wiping their eyelids and cloacas. They will act as the controllers of the conservation genomics team.It’s all about how… these specimens are [symptomatic] It is different from other specimens in the environment in terms of microbial community.
Despite months of testing, why is the pathogen of the disease so elusive?
It’s not just a question of what makes a given bird sick… It’s much harder to diagnose a problem that coexists across a wide range of geography, wide time scales, and a large number of species.
What do all these specimens have in common that are different from healthy birds?For example, we know that many mycoplasma test positive [bacteria], But we know that many healthy birds test positive for mycoplasma. Not all birds that we believe are related to this incident have tested positive for Mycoplasma. Certain things may affect the nervous system of birds, which can also suppress their immune system, leading to secondary infections.
What do you think of the hypothesis related to the emergence of Brood X cicada?
There are multiple assumptions about the causes of potential driving events. Some tests were negative: West Nile virus, avian influenza, and Salmonella were negative. The cicada hypothesis is actually a set of hypotheses developed due to the very strong overlap between mortality events and the distribution of cicada brood X. Areas with a lot of cicadas seem to have a lot of deaths; areas with fewer cicadas seem to have lower deaths… We are always careful to say that in this case, the correlation is not causal-we also know that the June environment There are more chicks in Cicada, at the peak of cicadas, more than in July and August.
This is still a hypothesis on the table, but now it is much less likely, because we have discovered the dead-affected area where Brood X does not appear.
Many of the early reports appeared to come from amateur birdwatchers and community members, and ornithologists took some time to take these reports seriously. Does this explain the relationship between professional scientists and community science?
I’m sure it is. A lot of my research is related to community science data, but even I am skeptical of community science. I think this is a lesson for me, and we as scientists must do better to listen to the opinions of the community.
When we agree with what they say, or when community scientists do what we want them to do, it is easy to predict their importance. If so, when community scientists observe things before we make observations, that’s another matter entirely. Then the old bastard scientist among us came in.
What have you learned from this experience?
Frankly, I’m a little ashamed, I was such an arrogant bastard at first. This is a real lesson about humility for me. We did this with COVID: we often pretend that things we can’t see have not happened.
The biggest question about this incident still exists. Do you think we will get the answer?
I think it will be resolved. For me, the biggest problem to be solved first is whether it is caused by an infectious disease or by a toxin. Everyone scrambled to put their bird feeder back in place.I heard too much language and too much pressure-“When can I start feeding the birds again?” My answer is always “Let’s wait and see [the U.S. Geological Survey’s National Wildlife Health Center] Say. “If it is an infectious disease and we care about birds, we should not put the feeder back.
It is also very important to know whether it is an environmental toxin. Why will we see it in 2021-so many? “Will we see it again in the next breeding season?” is another important unanswered question.
You mentioned Guidance from the U.S. Geological Survey People in some states in the Mid-Atlantic, Southeast, and Midwest should cancel their bird feeders. What else can people do?
The most important thing people can do is submit their observations.I have received reports from people, whether through Bird Mortality Report Form Colleagues from different states, these states are not in the expected affected area. We need to resolve whether our scope of influence is actually accurate. So, for example, if this happens in Texas and there is no Brood X cicada in Texas, this is the real problem with the cicada hypothesis. Bird lovers should submit their observations and take photos and videos of a large number of birds.