The sky is falling: birds and hail

The season of the summer disaster movie is upon us: Godzilla is stomping San Francisco, and I’m sure we’re all eagerly anticipating the premiere of Sharknado 2. To liven up the cinemas a bit, as a relief from the overabundance of sequels (I mean really, Sharknado 2!), I would like to propose a new genre mash-up: the animated talking birds disaster movie. It would be like those dancing penguin movies, or the solemn-looking owl movie (I have seen none of these…), plus disasters. The first one could be called Hailstorm!

It would not be a children’s movie. It would be terrifying.

It hailed on us a few days ago for about half an hour. The hail was mostly small, not larger than 1 cm in diameter, and the only animal reaction I saw was a decidedly alarmed chickaree—although to be fair, chickarees almost always look alarmed. I saw no evidence of damage afterwards; all of the junco nests we were monitoring weathered the storm just fine.

We hid in our tents.

You know the hail isn’t too bad when you can safely hide from it in a tent.

But sometimes hail is a sharper-fanged beast.

Hail is ice falling from a great height, so it isn’t surprising that it can do real damage, especially to small, delicate birds. A relatively minor hailstorm (stones mostly less than 2 cm in diameter, and the storm lasting only 6 minutes) injured ~10% of a group of Great-tailed Grackles and Common Starlings as they roosted on night in Texas. Birds who roosted lower in the trees fared better than those who roosted higher, presumably because the branches protected them (Hall & Harvey 2007). This is probably what protected our junco nests too: I’m sure even our small hail stones could have done damage to the thin skull of a young nestling, but junco nests are generally somewhat hidden under vegetation.

Junco nestling, the day after the hailstorm: doing fine.

Junco nestling, the day after the hailstorm: doing fine.

Hail poses a greater threat to birds without shelter. Dow (1972) describes a storm near Queensland, Australia: “At 18:25 a deluge of rain issued from pitch-black clouds across a pale-green sky… The rain and hail, driven hard from the south-west, was accompanied by gusty winds.” The nest morning he found “at least eighteen trees had been struck by lightning, leaving jagged splintered stumps.” Dow was studying Noisy Miners, and he found that although several nests had been “badly flattened or smashed,” none of his adults appeared to have been injured.

This Noisy Miner kind of looks like a hail stone. Photo by Leo*

This Noisy Miner kind of looks like a hail stone.
Photo by Leo*

The hail casualties were not the tree-dwelling miners, but rather, the open-water-dwelling Black-winged Stilts, who had no protection. He estimated that 20% of the local population of stilts was killed in the storm.

Even more exposed than stilts on open water are birds in flight. After a storm featuring lightning and hail in Arkansas, Roth (1976) surveyed the ducks that had been flying and then brought down by the storm. Many of them had sustained fractures and bruises from the hail, as you might expect. Some had become covered in ice, the same weather conditions that create hail coating the feathers of the flying birds in a layer of ice. Four dead ducks recovered after a lightning flash had feathers that were “kinky, as if burned.” Impressively, a few “dazed” birds found on the ground recovered rapidly and escaped their observers. Even plunging from the sky in the midst of hail and lightning can’t keep some birds down.

The most dramatic account that I found comes from Smith & Webster (1955), of the effects of a storm in Alberta, Canada, that mixed 75 mph winds with hail stones larger than golf balls.

Hail stones larger than gold balls (from North Dakota, not Alberta, but you get the idea). Photo by SnoShuu*

Hail stones larger than gold balls (from North Dakota, not Alberta, but you get the idea).
Photo by SnoShuu*

They write: “Song-birds, hawks, owls, crows, grouse, coots, grebes and ducks, both adult and juvenile, were wiped out. Adult ducks of all species as well as their young littered the potholes and lakes in the storm’s path.” Vegetation couldn’t shelter the birds from this storm because the vegetation itself was destroyed: “Vegetation was shredded beyond recognition and beaten into the earth. Trees were bare of leaves and small branches, the bark on the southwest side of the trees had been torn away or deeply gouged…”

Lest you think the birds overly fragile, it’s worth noting that “a 600-pound sow and several calves” were also killed in the storm, and cars “were so badly dented that the bodies were beyond repair.”

Still, a ground survey of the areas that had suffered heavy damage found survivors: two adult ducks and five ducklings had made it through, somehow.

So tough.

So tough.

I’ll be happy to stick with my little hailstorms, I think.

hail1

*Photos obtained from Flickr and used via Creative Commons. Many thanks to these photographers for using Creative Commons!

References:

Dow D. 1972. Effect of a catastrophic hailstorm on bird populations. Emu 72:22-23.

Hall DW, Harvey TM. 2007. Mortality at a night roost of Great-tailed Grackles and European Starlings during a spring hail storm. The Wilson Journal of Ornithology 119:309-312.

Roth R. 1976. Effects of a severe thunderstorm on airborne ducks. The Wilson Bulletin 88:654-656.

Smith AG, Webster HR. 1955. Effects of hail storms on waterfowl populations in Alberta, Canada: 1953. The Journal of Widlife Management 19:368-374.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s