But I won't say it's not beautiful! It is lovely out for the most part. Even if I can't breathe and everything itches!
Nobody read my last journal entry, which I'll blame myself for because I messed up the link, but I don't know. I didn't even get any comments that the link didn't work so maybe Facebook is just muting me. I'm sure it was "THE ALGO" (and posting the wrong link entirely) and not any indifference on your lovely parts. But now I'm very tempted to recycle some of the photos I shared last time, because we went on a very cool walk down by Elliot Bay and I saw lots of cute lil gulls.
This weekend we are planning to go looking for a heronry. A heronry is what you'd expect. Like a nursery but more birds. A bunch of herons like to build their nests atop trees near the Ballard Locks. The males go and find a nice spot. Then they hang out and wait to lure the females closer. When a viable mate happens by, the males will start stretching their necks all sexy-like and start making clicking noises with their bills. Interested females show up and the males and females start stretching their necks and clicking together in a series of displays.
If it keeps going well, a male will start bringing sticks for the female, who will construct a giant ass nest for some giant ass birdies. Eventually there are eggs and eventually the eggs hatch and OMG baby dinos!!!
Hopefully we'll get to see a bit. On Wedesday we did see two great blue herons at the pond flying around. I could not say if they were enemies or lovers or possibly enemies-to-lovers, but it was cool.
Anyways, now that you've made it here, sorry to let you know this isn't actually one of those pleasant pictures and random thoughts about the week posts. Today I'm going to talk about invasive species.
This has evolved from an internet rant after I made an apparently bold statement in defense of house sparrows (and starlings). The vitriolic hatred people have for specific animals is very distasteful to me. It's one thing to need to control a population but some people get literal pleasure from hurting undesirable birds, and that is basically everything that's wrong with humans in a nutshell. In fact there's a lot of the ugly side in these conservation debates, and I think there needs to be a lot of reflection whenever we talk about such loaded concepts.
 |
| Invasive, a bit of a pest, but smart and pretty |
This particular discussion was about House Sparrows. So let me set the scene here.
House Sparrows are common birds in Europe. They're noisy, gregarious and about as clever as most "pest birds" turn out to be. They are super-generalists, extremely adaptable and well adjusted to human behavior. They often nest in our structures and feed on bugs and grain from our agriculture. Over the course of European colonization, they have expanded their range around the world.
They were introduced into the United States in the 1850s. At the time, many people thought it was an superlative idea to introduce flora and fauna from their homeland into the United States to share the benefits of these species worldwide. Many European birds made the trip across the Atlantic (most of whom died) and the survivors were released into the United States in the hopes of jump-starting populations here. Most of them died.
House Sparrows were a little different. Like Starlings would a few generations later, House Sparrows thrived in their new environment. They are birds that live where humans live. And there we were!
The relationship soured quickly. Even by the time Starlings were released in the US in the 1890s, House Sparrows were seen as pests and much worse.
House sparrows do some pretty brutal shit. They will kill bluebirds in their nests to claim the nests. Sometimes even using the bluebird corpses as part of the nest (though I'll note that this behavior is hardly exclusive to them). This has led to the somewhat natural assumption that they are to blame for collapses of certain native populations. Which sets up the one space where conservationists get to feel really nasty towards an animal: that criminal low life animal is non-native and it's stealing our jobs and assaulting our women! Wait, wait. Wrong speech. But you know what I mean.
While I am in favor of preserving biodiversity, and I do try to cultivate native flora and fauna, I am hesitant to simplify this very complicated discussion into a simplistic duality. I don't want blackberries in my yard. But dandelions, for instance, are great for early pollinators and not considered invasive by many scientists even though they are immigrants.
Dandelions typically show up on disturbed soil (places where humans are), cracks in sidewalks, and in non-native lawns. They don't seem to invade the wilderness as often. They condition the soil. They provide food for many species. And, probably more to the point, a lot of people like them. We have positive memories of blowing them into the breeze. So... not natural, but not invasive. Sort of.
In some places and by some groups they are considered invasive. In other places people are encouraged to hold off on weeding for the sake of the bees.
It's not simple.
Populations move all the time. Ranges shift and expand. When is that shift "a problem" and when is it just nature.
I also wonder what the end goal is in terms of combating invasives and preserving natives. Is that even entirely possible? If we have modified the environment locally enough that the native flora and fauna are no longer ideally adapted to it, then what's the right solution? It doesn't seem like humans on average are willing to do what's necessary to go back to where we started, so what are we wanting to do?
I do think that diversity is important. And maybe that's the end goal. But I definitely think it's complicated.
Yes, we seen the havoc a house sparrow can wreak on a bluebird nest. That alone doesn't mean that we know that overall house sparrow populations are categorically at fault for the peril of our native birds. Anecdote is tricky. You can read through comment sections from bird lovers everywhere and see several anecdotes from other people who see house sparrows happily coexisting with other species. Are they missing something? Likely. Observation can be distorted and can only give us a tiny slice without clear interpretation.
We also may not like the brutality we see. I don't love seeing a peregrine tear apart a pigeon, although I'm abstractly happy that feral pigeons in cities provide sustenance for falcons to move into urban environments as needed.
But the unpleasantness doesn't speak to the long-term impact in an ecological sense. We don't always have the tools to interpret what we've seen or the ability to abstract simple observation to a macro level. Our guts can be wrong, and this is why there is research.
To be clear, sometimes the introduction of an invasive species can be unequivocally devastating. Particularly in island communities, introductions of predators like cats and rats have caused wide extinctions and disruptions, as these endemic populations often have no evolved responses to predators. Animals like goats introduced to island populations can also destroy the landscape. The arrival of the mosquito in Hawaii was devastating! These are things with clear causes and fixes. But, often it's a bit mushier.
On house sparrows, it's a bit mixed. It seems to be location and context specific.
In some places, removal of House Sparrows contributes to rebound of bird populations (Eastern Bluebirds, specifically) and other times it doesn't impact a nearby native species. And in many cases, it's hard to tell because House Sparrows follow humans - anywhere there are House Sparrows, there's a lot of anthropogenic change.
Eastern and Western Bluebird populations tanked in the 1970s. A program that mixed nest boxes, growth of habitat, and removal of non-native competitors helped them rebound. Controlling house sparrows has been helpful in this case, albeit not enough on its own.
We know that house sparrows will aggressively compete for nest boxes with native cavity nesters. We also know that - unlike bluebirds - they will allow others of their species to nest nearby, meaning an ill managed nest box trail can lead to massive increase of house sparrows at the cost of bluebirds.
It makes sense to deter or evict house sparrows from nest boxes in this context. But fundamentally the crisis was caused by reduced habitat, pesticides, and changes in agricultural practices. House Sparrows made it harder to take corrective action, but the crisis seems likely to have occurred in their absence.
In 2022 a Mountain Bluebird conference reported that mountain bluebirds continue to decline steeply - an estimated 34% in the last 15 years - despite controlling for House Sparrows. Loss of habitation is again the main culprit. Another emerging concern is climate change, which may render their breeding range unusable if temperatures rise another Centigrade.
In 2025, scientists estimated the driving causes of bluebird decline were habitat loss/degradations/fragmentation, declining insect populations, climate stressors, and extreme weather.
In fact, house sparrows who are stealing nest boxes have been contributing to science in a morbid way: citizen scientists began shipping nest-box sparrow eggs back to researchers who have been testing the eggs for heavy metals. Eggs removed from nest boxes turned out to have unexpectedly high concentrations of heavy metals.
Given house sparrow ranges, it's likely that they were exposed to these metals from nearby sources - either feeders or areas very close to the nest. That's of concern for more than the invading sparrows!
(Incidentally, measurements of metal levels in house sparrows are also used as markers of risk for children in potentially contaminated areas - unprotected birds do a ton of heavy lifting on our behalf. House sparrows are actually one of the most studied birds in history for multiple purposes, including conservation. Pigeons, of course, are another)
In general, American birds are declining regardless of starlings and house sparrows. A recent study found a net loss of nearly 3 billion birds, roughly 1/3 of the breeding population, since 1970. Habitat loss is always the number one reason, followed by habitat degradation and fragmentation. Pesticides both directly kill birds through ingestion and indirectly by destroying their food base. One study put pesticide related deaths at 2.7 million deaths in Canada alone.
And, well, humans:
When house sparrows do have a measurable impact on a population, this often come down to human behavior. Bluebirds and house sparrows don't actually prefer the same nesting sites given unlimited resources. Bluebirds most often frequented burned pine savannas, mature open woods, and forests. As those are replaced by human living spaces, they have come into suburban areas and agricultural fields. House sparrows have coevolved to live near humans and look for human structures. They are less commonly found in areas away from us.
Proper management when putting up a bluebird nesting box includes putting it well away from where house sparrows like to nest. Using specific materials can discourage house sparrows from nesting boxes. Feeding opportunities and bird baths will also draw them to nest sites. This is something humans control. It's our actions often bring these birds together. Just like when we don't manage our trash and this draws racoons or other predators. The birds are often simply second and third order effects of our choices.
Nor do birds have to be invasive to out-compete or negatively impact a native species. Many native birds aggressively attack other native birds. The scarcer resources are, the more territorial and violent they may become. Many cavity nesters will usurp nests from other species, dispose of the eggs, and eat the young. Larger woodpeckers can terrorize smaller birds like blue tits, and even starlings. Even fairly fierce birds are at risk of losing their eggs either to a competitor or a predator.
 |
| This bro got a spear more or less to catch all manner of noms |
And of course, predators kill to live. Most birds predate on insects, fish, small mammals, invertebrates and other birds. Very few birds rock the vegan lifestyle.
The behavior itself is "natural" as these things go. The natural world is violent. The behavior is not the issue. It's whether it reaches a certain tipping point in the balance of populations. And we have to be able to measure that impact and make specific judgment calls.
Barred Owls, having expanded their range West, are contributing to declines in Screech Owls and spotted owls. They are identified as a primary factor in the 75% decline of the spotted owl. In response, US Fish and Wildlife Services announced a plan to cull half a million Barred Owls, despite these owls being native birds protected by the Migratory Bird Act. The Senate approved of that plan last fall despite objections and ongoing controversy.
House wrens outcompete Bewick's Wrens in the Eastern US by destroying their eggs and interrupting their nesting. They will destroy eggs and kill the young of several other cavity nesters, including chickadees and bluebirds. They do this to the extent that they also need to be managed (more cautiously because they happen to be protected by the Migratory Bird Act) when setting up bluebird nest boxes.
In turn Bewick's Wrens in the west are contributing to declines of Pacific Wrens due to aggressively outcompeting them in the ever-increasing urban areas.
On the Pacific Coast, crows, ravens and Steller's Jays have threatened the endangered Marbled Murrelet because they are following people in the national parks where the Murrelet needs to nest. Once in the parks, they will eat Marbled Murrelet eggs and occasionally kill the adults. Here, the primary conservation strategy has been to reduce available food for these birds in National Parks. The Crumb Clean Campaign took a multipronged approach to eliminate available food in areas where Murrelets nested. As a result, the ranges of Steller's Jays and Marbled Murrelets overlap less. Adding locking trash cans, food lockers, and dishwashing stations helped disperse concentrations of corvids from those areas.
Native cowbirds expanding their range contributed to the declines of the Kirtland's Warber (though again human activity was the greater share). Cowbirds are brood parasites, another easy target for moral outrage and condemnation, and they seemed to particularly lay their eggs in Kirtland Warbler's nests. While cowbird chicks don't kill their foster siblings like some other brood parasites, they often outcompete them for resources within the nest. It's unclear whether that results in significant losses of fledgling hosts, but it seems like the most successful number of nest-mates for a cowbird chick is two and any additional fledglings might not get the resources to survive.
Kirtland's Warblers will likely always need human intervention to thrive in the world we've created from theirs. Kirtland's warblers require large areas of young jack pine. If it is too young or too old, it is not suitable. If it is too tall or too short, it is not usable. Before human fire suppression, this was easily supplied by natural burn cycles, but as we intervened in these cycles, the "just right" conditions for many birds ceased to exist without conscious choice.
Kirtland's warblers are considered "conservation reliant." Their specialized breeding requirements mean constant intervention with controlled burns or specific plantings in order for this species to continue to survive. While it is considered a huge success story, the population is declining again after its huge rebound. In the last five years, it has declined by 30%. This is largely due to tradeoffs between land managers, economic needs, and competing conservation needs. (Not cowbirds)
This is a story that plays out again and again. While active aggressive and parasitism from other species serves as an exacerbating issue (and symptom), it is often that we alter the environment in such unpredictable and drastic ways that we invite more generalist birds to out compete the specialists.
Having brought the chaos that pits these species against each other, we are now continuing to play God trying to reclaim an Edenic equilibrium that we ourselves upset. Many of the species that we've "rescued" from extinction will need pretty much ongoing support to live in the new world we've created. We're making different choices than those who brought starlings and house sparrows into the New World, but we are still ultimately projecting our preferences onto the natural world and altering it to our tastes.
This is not a criticism. It's a selfish issue. We are part of one of the great mass extinctions in the natural history of this planet. We are already beginning to see some of the impacts of habitat destruction and pollution. It would be naive to imagine that this is a positive long-term situation for the human race. Often preserving a native species, even at a cost, is ultimately creating conditions that make life more sustainable and pleasurable for all of us. Whether you feel that we owe it to the natural world, we certainly benefit in ways we are only starting to unravel.
 |
| Invasive as all get out |
The extent of change we are causing is staggering. And things are actually getting worse instead of better in many areas. There is so much that needs to be done to reverse this trajectory. This is where vituperation against these "invasive" birds really gets me: wasting passion and energy on these birds is diverting energy from more productive interventions. Perhaps we hate them because they hold a mirror to ourselves a bit too well.
Most tellingly, even the house sparrow and starling population are declining in the United States (more so in their native ranges). A 2026 study found that 122 species of bird are experiencing accelerating declines, including the most populous birds: crows, starlings, house sparrows and grackles. These were concentrated in areas where agriculture was high intensity, bringing home that human connection.
As Cornell's Kenneth Rosen said, "if our environment cannot support healthy populations of these extreme generalists and extremely adaptable species that are tolerant of humans, then that is a very strong indicator that the environment is also toxic to humans and all other life.”"
Perhaps instead of treating house sparrows and starlings as the problems, we see them as alarm bells for the planet at large. They are more like us than we like to believe and where they struggle, we likely will as well.
No comments:
Post a Comment