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The Cradle Robbers

werwrwe

I wonder if you’ve ever noticed something particular to mountain rest-stops, ski resort parking lots, state or national park campgrounds, or any other place where humans congregate in our typically distasteful, gregarious manner. Not the motor homes, not the camera adorned visitors, not the profound lack of respect for the cleanliness of the beautiful locales. Ever notice how many birds are around?

Now these aren’t just any birds, simply there because you are in beautiful, natural setting. In the alpine regions of the Cascades, the Olympics, or any other range in a temperate climate for that matter, bird diversity is relatively low. Yes, it seems so wild you expect birds to be dripping off the trees. In truth when we visit the mountains, species are distributed into territories to breed efficiently before the seasons change. Birders go to the mountains for very specific, highland birds, not to rack up a species list. So no, there aren’t a bevy of species skulking on the edges of our human insinuated habitats. Mostly, there’s one group of birds. Corvids.

Corvids, for the uninitiated, are the family of birds that encompass crows, jays, magpies, ravens, and a few other species. They are on every continent except Antarctica, but their diversity is centered in the New World and Asia. Despite their size and relative lack of musical talent (to our ears), they are songbirds. In fact the Common Raven (Corvus corax) is the largest member of the order in North America. They all have rictal bristles (except Pinon Jays), feathers which sprout near the nostrils and grow towards the tip of the bill. They are typically quite stout birds with heavy utilitarian bills and strong feet, which aid them in being generalists of whatever environment they inhabit. There are a lot of comparisons to make with apes, as we have very multi-purpose teeth, have hands to manipulate things, and also have large brains. Ah yes, those large brains; on the brain to body mass index corvids are right up there with apes and cetaceans.

Many of us know crows and ravens particularly for their intelligence. Some people find members of the family extremely annoying as a result, it’s true that their intelligence can make them pests. I’ve seen crows dig up my freshly planted vegetable garden, presumably because they watched me dig holes and put things in the soil. I dislike the comparisons of intelligence that people inevitably make with other animals, we are so damned arrogant, but it’s decent frame of reference. New Caledonian crows, famous for their tool making, are probably one the smartest non-hominid animals in the world. I’m not going to tell you about the crows of New Caledonia, or any other tool use in corvid for that matter. The topic is as lengthy as it is mesmerizing. The take away is that crows, jays, ravens, and their kin use their intelligence well, especially when related to food.

Of course, regardless of the trouble corvids can create, I love the little buggers. They never cease to amaze. However, in the alpine, I have mixed feelings about how often and where I see them.

When I’ve guided in the past, taking people to Paradise at Mount Rainier or Hurricane Ridge in the Olympics, I consistently expect to see a common raven, a gray jay, or a Clark’s nutcracker, maybe a Steller’s jay too. This is great for a guide who wants to easily show off some native species, but these corvids aren’t there because they want to help a brother out. Our presence attracts them, because our overabundance of calories and in turn wastefulness means opportunity. In fancy terms, picnic areas and national park parking lots are the epitome of anthropogenic food sources.

There’s a lot of ways this discussion can go. Gray jays are notorious for their willingness to alight on your hand or food, often unbidden. They’ll even drift toward anthropogenic food sources in the middle of nowhere if they’ve had a few profitable experiences with people. I once sat on a summit that I presumed seldom had people (no trail to it existed and it was literally miles from the nearest easily passable road), only to have a gray jay land directly on my sandwich when I wasn’t looking. I won’t lie, I’ve fed gray jays, Clark’s nutcrackers, and ravens in the past (for shame), but I’ve stopped (I swear). Almost all of us enjoy contact with animals, (I’m gross though and have let pigeons in a Thai city land on me) and these bold jays offer a great opportunity for that. That said, you really shouldn’t be feeding them.

A poor argument for not feeding corvids, and one I’ve heard too many times, is that if you feed them, they’ll become habituated and have trouble fending for themselves. This is a non-issue, they’re too smart for that, but it’s true for other animals; feeding foxes at Mt. Rainier creates many casualties because they beg for handouts on the winding, shoulderless roads. The best reason to not feed corvids your snacks is that they aren’t good for them. If your cheetos, white bread, and salami aren’t healthy for you, why in the world would you give it to a bird? I fully submit that we are being taken advantage of as a food source by the birds and that we won’t be able to completely eliminate their presence and sneaky snatches, but you can stop feeding them.

Another more compelling reason I’ve regurgitated many times, relates to another of their food habits. They are excellent nest predators and the general assumption is that their presence has a heavy impact on songbird populations in places where they unnaturally congregate for anthropogenic food sources. This appear to be clear logic, but since I myself have said this, I might as well see if it’s true.

Turns out it’s not that simple.

The issue with making logical leaps like this are simple. Yes, it’s likely that more nest predators mean more predations. However, does that actually mean that they have a negative impact on overall survivorship of the birds they predate? So far as anyone can tell, not statistically.

In various studies, looking at a variety of corvid species, there didn’t seem to be a direct correlation between nest failures and increased presence of corvids. In several studies, several of which were done by John Marzluff of the University of Washington (a corvid expert), some birds didn’t even behave differently as a result of human presence. Steller’s jays, which heavily predate on eggs and nestlings of songbirds, didn’t appear to distribute any differently or travel long distances to get at human food. Crows and ravens were much more likely to, but didn’t show any increased impact when they traveled to areas with anthropogenic food (in other words a nest predation was relatively incidental, not actively worked for when human food was there).

In Britain and much of Europe, there’s been a steep decline in songbirds and many people have been prone to blame their corvids for the problem. Human’s are spectacularly good at blaming other species before they presume they could be the problem. Unlike the United States, where wild areas abound, the vast majority of Europe has been heavily altered for some time. In Britain it was possible for researchers to find managed land that provided excellent study areas, land that was with or without the various jackdaws, rooks, ravens, magpies, and jays that could be causing decline (which were being systematically “removed” by people) and other areas with them. Once again, there didn’t seem to be any impressive difference in nest survival (which ultimately is different than overall survivorship of a bird).

Seattle is a great place to explore these ideas, which Marzluff has done extensively. We have many small pockets of habitat, which in some sense could be ecological traps for nesting birds. A small band of forest (native or otherwise), say Ravenna park in Seattle, is full of decent nesting habitat for songbirds but every corvid, accipiter, and small mammal in the area knows where to look for high nutrient eggs. As we urbanize, it’s important to think on this scale; density done the wrong way can mean less green space decreasing diversity even more, making it harder for the birds that persist.

Gray jays, which are the most conspicuous opportunists of the campground, parking lot, or picnic area didn’t seem to have any different impact. They are well known for nest predation too. Several studies demonstrate that not only do gray jays increase their numbers in the presence of humans but that they spend more time on edges, generally our choice places to eat lunch or park our car. It stands to reason that the birds do negatively impact nesting in those areas. Again, the jury is out on whether increased presences has real implications for songbird populations. There’s a chance that nesting behavior is much more plastic in response to habitat or threats anyway. Gosh, so complicated.

Let’s also not forget that corvids are not the only predators out there. Many studies mentioned that they actually had higher records of squirrel species predating nests. Chipmunks took a heavy toll on studies conducted in the Pacific Northwest. I’m not looking for a scapegoat, merely continuing to point out that there’s never simplicity for studies.

Whether or not corvids are to “blame” is only part of the story. By looking at the distribution and behavior of predators, we can also look as how this influences the species they predate on. In turn, this can help guide forest management; showing positively that a threated species has lower fecundity in forests where logging creates obvious and copious edge areas.

I love a question unanswered because it leaves me wondering while I am out in the greater world. The bottom line should be that we don’t really need to be feeding or encouraging corvids to hang around. A subtext is that we don’t actually know what impact it may have. Possibly there are larger questions in the world, but I’d ask you what you like more: watching a curious gray jay or pondering climate change? I like both but sometimes I appreciate less imposing ideas. Just because you might have some guilt over impact doesn’t mean you can’t take a second to appreciate the smaller world too.

1 Comment so far

  1. Pingback: A 2013 (Photographic) Year in Review | Wingtrip

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