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I live in Northern Virginia, the portion of Virginia that abuts DC and Maryland. We had a particularly large emergence of 17-year Brood X cicadas this past summer (summer 2021). I was here for the 2004 and the 1987 emergences and both seemed relatively meh compared to this summer's. (Personal impression, not actual data.)

My personal impression also is that birds and other small critters had a banquet, and turned up their noses at bird seed. This, however, is just an impression. I also have the impression from anecdotes I heard from my neighbors that there was an unusual number of snakes, including copperheads (our only venomous species here) in evidence.

As I say, all this is impressionistic. Is there actual data on population upsurges of other species coincident with the 17 year cicada emergences? In particular, was the effect (if any) particularly large this summer, and if so, was any part attributable to other factors, such as hotter weather than in earlier years?

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  • I'm sure there is data - there certainly is for "mast" years in beech forest where the trees produce massive amounts of seed and get an uptick in animals that feed on them, followed by an uptick in predatory species in turn.
    – bob1
    Oct 4 at 2:40
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    Population Responses of Peromyscus leucopus and Blarina brevicauda to Emergence of Periodical Cicadas David T. Krohne, Theodore J. Couillard and John C. Riddle The American Midland Naturalist Vol. 126, No. 2 (Oct., 1991), pp. 317-321 (5 pages) might be a start...
    – Jon Custer
    Oct 4 at 16:43
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Web of Science turns up some 143 papers on 'cicada emergence' across all search fields. There are a dozen or so that focus on the impact of the emergence on various predators, and a variety that focus more on the impact of the emergent biomass on the environment.

Lets start with a review article from 1995 by Williams and Simon. Here they state

Possibly the most important ecosystem function of periodical cicada emergence may be providing increased energy and nutrients to predators. ... In periodical cicada emergence years, avian predators showed increased fledgling success (4, 34, 1 16), nestling biomass ( 1 16), and clutch numbers and sizes (4, 34, 85). ... Krohne et al (60) found that periodical cicadas enhanced reproduction of some mammalian predators (e.g. shrews, Blarina spp.), but not others (e.g. mice, Peromyscus spp.). Hahus & Smith (29) also found that Blarina, Peromyscus, and Microtus (voles) incorporated periodical cicadas into their diet, but cicada abundance seemed to produce increased intake of arthropods only for Peromyscus.

Certainly lots of things eat cicadas, and their primary predation avoidance method is to 'satiate' the predators - too many cicadas, not enough eaters. The review article above notes that

Ultimately, predators consumed only an estimated 15-40% of the cicada population, and much of that probably occurred after cicadas had reproduced.

A study focused on the impact on rodents states

Data from a non-emergence year revealed no differences other than the presence of periodical cicadas that could explain the 50% higher relative densities of P. leucopus in the emergence year.

Or, white-footed mice love to eat cicadas and their population booms that year. Nothing is said about long term dynamics.

An article on bats by Storm and Whitaker notes that

Although periodical cicadas constituted a fair amount of the diet during the emergence, the dietary diversity of big brown bats during the emergence was similar to that of non-cicada years.

but makes no statements on the impact on population because of the availability of the cicadas. They don't specifically hunt them down, but will eat them when they find one.

An article by Koenig and Liebhold makes the statement that

Here we show that periodical cicada emergences appear to set populations of potential avian predators on numerical trajectories that result in significantly lower potential predation pressure during the subsequent emergence.

The same authors note in a more detailed paper on avian populations that

These results suggest that the pulses of resources available at 13- or 17-year intervals when periodical cicadas emerge have significant demographic effects on key avian predators, mostly during or immediately after emergences, but in some cases apparently years following emergence events.

with some species showing lower population numbers in the years before emergences (wood thrushes and mockingbirds), while cardinals and house sparrows showed higher populations.

Summary: lots of things eat cicadas, but can't eat them all. Populations of various predators do change as a result of all that food. That last article is perhaps the most interesting, where long-term effects (on the order of the cicada cycle) are noted on various bird species.

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    Thanks. Just what I was loking for. As an aside, cicadas appeared on the menus of several restaurants in my area.
    – ab2
    Oct 6 at 22:28
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    @ab2 - but did you eat enough to impact their numbers???
    – Jon Custer
    Oct 6 at 23:58
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    No, I am trying to go vegetarian. My cat ate a few and threw up.
    – ab2
    Oct 7 at 1:53

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