BioBrevia: Around the World in 6,042 Birds

ʻIʻiwi (Drepanis coccinea)

Photo: Philina English

Last year was a record-breaking one in competitive birding. In late December, I reported on the new Big Day record set in Ecuador, but another, even more monumental record was broken in 2015. An astounding 6,042 species of birds were seen by Noah Strycker between January 1 and December 31 last year! That shattered the previous record by more than 1,500 species. You can read all about the year-long chase here.

Damsels in Drag

A male (top) and ovipositing andromorph female Taiga Bluet (Coenagrion resolutum)

Photo: D Gordon E Robertson (Wikimedia Commons)

It's midsummer, early evening, and I'm sitting in my canoe, surrounded by swarming damsels. From my boat, wedged among the Broad-leaved Cattail (Typha latifolia), White Water Lily (Nymphaea odorata), Bullhead Pond Lily (Nuphar lutea), European Frog-bit (Hydrocharis morsus-ranae), Watersheild (Brasenia schreberi), and a slightly bewildering assortment of rushes and sedges, I watch the comings and goings of at least 14 different species. I count four spreadwings (Lestes spp.), two dancers (Argia spp.), the colourful Eastern Forktail (Ischura verticalis) and the diminutive Sedge Sprite (Nehalennia irene). Then there are the bluets, my favourites being the beautiful yellow male Vesper Bluets (Enallagma vesperum), which as their name suggests, are vespertinal indeed. And there is the Orange Bluet (Enallagma signatum), Skimming Bluet (Enallagma geminatum), Northern Bluet (Enallagma cyanthigerum), and perhaps one or two more species that require a close examination in the hand to identify with certainty.

This lakeside marsh has a nice variety of species, but the diversity of colours is even greater because all of the damselflies here are sexually dichromatic, males and females are different colours. In sexually dichromatic damsels, it's usually the males that are brightest, more strikingly patterned, than their female counterparts. Usually, but not always. Sometimes females are just as colourful as males. In certain species, some females in a population closely resemble males (andromorph females), while others wear more subdued hues, making them easy to distinguish from males (gynomorph females). This pattern is called female-limited polymorphism, and it has evolved among many different damselfly lineages, including among most of the ones flying around my canoe.

But why has it evolved in the first place? The most favored hypotheses among odonatologists is that female-limited polymorphism has come about as a way for females to avoid sexual harassment from males. Constant sexual harassment can be problematic for females, making them more susceptible to depredation. That's because the normally cryptically-coloured girls become far more conspicuous when pursued by or attached to a brightly coloured guy. Constant harassment may also impede a female's ability to hunt, which could influence the quality or quantity of the eggs she might lay, or even reduce her lifespan.

Certain species are exposed to harassment much more frequently than others. Harassment isn't a constant problem for females of territorial species. Ebony Jewelwing (Calopteryx maculate) males, for example, establish a territory along a wooded stretch of stream. The male patrols a small parcel of waterfront real estate, chasing off other males, and wooing passing females with their iridescent bodies and ritualized displays of their jet black wings. In the case of Ebony Jewelwings and other territorial species, females can avoid unwanted harassment from males by simply steering clear of their territories. Harassment is a big problem for so-called scramble mating species, such as the Taiga Bluet (Coenagrion resolutum). These damselflies forego establishing and holding territories all together. Instead, males hang out around ponds, and chase virtually every female that comes near, attempting to catch and mate with them before other males do. In the case of Taiga Bluets and other scramble mating species, its much more difficult for females to go about unaccosted, because randy males may be hiding behind any cattail. Indeed, some male damselflies are seemingly always on the prowl for mates, and are very indiscriminate about who they try to copulate with. Male Sedge Sprites, for example, attempt mattings not only with conspecific females (whether they are receptive or not), but also occasionally other males and even females of other species.

Most female damselflies, as far as is known, only need a single mating event to have all of her eggs fertilized, but may be subjected to many advances and forced matings by numerous males, particularly so in scramble-mating species. Thus, females get way more attention than is required, or no doubt wanted. That's not to say that females are entirely at the mercy of males. Sometimes a female that has been caught by a male simply will not adopt the mating "wheel" posture needed to be fertilized. In other cases, females will simply avoid males, or flee when pursued. Females may also be able to select which male's sperm they allow to fertilize their eggs, after copulations with assorted suitors.

Female-limited polymorphism is most common in scramble-mating species and it's a result of all that sexual harassment. Gynomorphs, those females that look different from males, still experience a high degree of the sexual harassment. But andromorphs, male-lookalike females, actually manage to avoid most harassment because males simply can't distinguish females from other males, most of the time. Andromorphs promote their deception further by not only physically resembling males, but also by acting like them. Andromorph female Sedge Sprites tend to do the same kind of chasing behaviours as males do. Heteromorphs don't do that.

Unlike Ebony Jewelwings and other territorial species, scramble-mating males don't appear to use their colourful markings to display to females. So why are they so colourful then? These males use them to signal to each other. It's a form of advertisement that effectively says, I'm not a suitable mating target. It's in the best interest of males to avoid mistaken mating interactions for a number of reasons, not the least of which is the missed mating opportunity. It's exactly this form of signaling that andromorph females play on to avoid unwanted advances.

I'm still left with a couple of questions as I watch the damselflies from my canoe. Why don't all females andromorphs? That way they could all avoid sexual harassment, right? Maybe so, but perhaps there is an advantage to being a gynomorph. Maybe sexual harassment is sometimes worth it if it increases your odds of getting the very best mate. Maybe the camouflage advantage of earth tone colouration, as opposed to bright blue, orange, yellow or purple, is worth the harassment cost. The answer to that one is yet to be determined, but given that polymorphism seems to be a stable characteristic in damselfly populations, both strategies must have their advantages. What about those andromorph females, are they at a disadvantage when it comes to finding a mate? Does being a damsel in drag mean you may never get the chance to hook up with a male? Well, it turns that andromorphs do just fine at finding mates. It seems that being an andromorph doesn't make you immune to the advances of all males, it just quells the tidal wave of orgiastic enthusiasm that can ruin and otherwise fine day at the marsh.

BioBrevia: Serendipitous Snowy Owl

Snowy Owl (Bubo scandiacus)

Photo: Mark Conboy

Entirely by accident, a Snowy Owl (Bubo scandiacus) was captured on a Montreal traffic camera, earlier this week. The footage was released today. Check out this short story and video from the Canadian Broadcasting Corporation.

BioBrevia: Amazing Galapagos

Swallow-tailed Gulls (Creagrus furcatus)

Photo: Philina English

Here's a beautiful look at the wildlife of Ecuador's Galapagos Islands, from irenaVision. A few of the archipelago's endemic species are shown, including Galapagos Tortoise (Geochelone nigra), Marine Iguana (Amblyrhynchus cristatus), Land Iguana (Conolophus subcristatus), Swallow-tailed Gull (Creagrus furcatus), the Galapagos subspecies of Short-eared Owl (Asio flammeus galapagoensis) and California Sea Lion (Zalophus californianus wollebaeki). Conspicuously absent, however, are the most historically important endemics, the mockingbirds and finches, which were so instrumental to Charles Darwin's early thoughts of natural selection. Enjoy.

BioBrevia: Introducing the Ninja Lanternshark

The newly described Ninja Lanternshark (Etmopterus benchleyi)

Photo: From Vasquesz et al 2015

A new species of lanternshark, whimsically named the Ninja Lanternshark (Etmopterus benchleyi), has been described in a paper by Vasquez et al in the Journal of the Ocean Science Foundation. Like the lanternsharks I've written about previously, the Ninja Lanternshark can glow, but it seems to have only a limited number of photophores.

Sanguivorous Stomoxys

Stable Fly (Stomoxys calcitrans)

Photo: Pavel Krok (Wikimedia Commons)

Biting flies are a fact of life in Canada. From spring snow melt until autumn freeze-up, mosquitoes, deer flies, horse flies, moose flies, snipe flies (Symphoromyia sp.), black flies and no-see-ums (Culicoides sp.) turn forests, wetlands and tundra into buzzing menageries of pain. Oh, how many litres of blood I have donated to the sanguivores of the north! I've lived and worked all over Canada's boreal forest, and the flies there are as bad as can possibly be imagined - actually sometimes they're worse. Presently though, I live in southern Canada, almost as far south as you can go and still be in the Great White North, 700 km from the boreal forest, but even here, on the shores of Lake Erie, the flies still torment me. There are mosquitos, and deer flies, and horse flies, including a particularly large species that I like to call the Darth Vader Fly (Tabanus atratus), but they're nothing like what I'm used to from in north country. Instead, the shores of the Great Lakes harbour yet another villain, one that's every bit as tenacious and often as abundant as its boreal couterparts: the Stable Fly (Stomoxys calcitrans).

Now I've been dealing with Stable Flies all my life, as a minor annoyance on any given fishing or canoe trip. But only recently have I found a place where a normal day in late summer or early fall entails braving swarms of thousands of the little bastards. That place is Long Point, on the north shore of Lake Erie, and I just happen to live there. After spending a summer feeding Stable Flies with generous helping of my blood, I wanted to understand why there are so many flies on Long Point.

Stable Flies are yet another unfortunate addition to the long list of Old World species that have been introduced to North America. That's right, they're not native, so if it wasn't for some damned fool who imported the little monstrosities, we'd be able to enjoy our summers with one less entomological menace. But alas, humans have a particular knack for ruining everything. The Stable Fly likely came to North America in association with livestock as early as the 1700's, and as its name suggests, it's associated with stables, barns, and farms in general. And its on farms that Stable Flies become a serious pest. They are blood suckers, and they can take so much blood from livestock so as to cause anemia, weight loss and reduced milk production. If that wasn't enough, they can potentially transmit lethal diseases like anthrax-causing bacteria, Bacillus anthracis.

Stable Flies are obligate sanguivores, females require not one, but  at least two complete blood meals to produce eggs. Males also bite, something that sets Stable Flies apart from almost all of our other biting flies, in which it's only the females that take blood. Indeed, Stable Flies are oddities within their own family, Muscidae. Most muscids suck up their food using soft, spongy mouthparts, a House Fly (Musca domestica) is a good example. Among our muscids, only the Stable Fly and another livestock pest (that doesn't attack humans), the Horn Fly (Siphona irritans) bite. Stable Fly bites are particularly painful because they don't inject their victims with anesthetic, like mosquitos so courteously do. Feeding primarily on livestock which, other than floppy ears and a whipping tail, have no way to keep the flies at bay, meaning that Stable Flies don't have to exercise subtlety when they bite because there is nothing  their victims can do to stop them anyhow. That's probably also why Stable Flies take their time sucking up blood: it takes about four minutes to consume a complete blood meal.

Thankfully, as anyone who has toiled among Stable Flies will know, these insidious insects fly low, focusing their bloody attacks on the legs and feet, generally sparing the rest of one's body (so dressing appropriately can be a simple and effective defense). But they also, from time to time, fly really high, they've been collected 1 km up and probably go much higher when swept away in weather systems. It's during these high-flying forays that Stable Flies disperse from their breeding sites, the rotting vegetation and manure of active feedlots and barnyards. Rotting vegetation elsewhere, like that which washes up on Great Lakes beaches or in wetlands can also be a source of Stable Flies, but it appears that livestock operations are by far the most important breeding grounds. During these dispersal events, they can form untold concentrations along the shores of the Great Lakes, including literally right in my own backyard. The reason they accumulate specifically along the Great Lakes may have to do with localized weather patterns, lake breezes.

Lake breezes are familiar to all who live on the Great Lakes. It's the lovely wind that blows onshore throughout the day, moderating summer temperatures, and making the intense humidity of July and August bearable. It's a localized phenomenon that can be thought of as a conveyor belt of air swirling above the lake and shoreline. The lake breeze begins as the morning sun heats the land adjacent to the lake. As it warms, air over land rises, often carrying with it a morning flight of Turkey Vultures (Cathartes aura), hawks, and an assortment of insects, including Stable Flies. The warmed, rising air, once it reaches a certain altitude, flows out over the lake. Vultures and hawks can exit the rising air masses at any time, but Stable Flies often remain trapped, so are pulled out over the lake with the flowing air. Now over the lake, the air begins to cool, descending and carrying with it those same flies. The rising air over land causes an area of low pressure to form, so that higher pressure lake air flows towards the shore, filling the low pressure void. This completes the cycle, the air that was once heated over land and that subsequently cooled and descended over the lake, finally flows back toward to shore. Those same Stable Flies, now well-travelled, ride back to the beach on the lake breeze, and there they accumulate.

Stable Flies aren't the only insects that get caught up in lake breeze cycles. Perhaps even more noticeable are lady beetles. I've been inundated at my Lake Erie home with countless thousands of Multicoloured Asian Lady Beetles (Harmonia axyridis). I've seen their colourful little carcasses wash ashore in unbelievable profusion, the ones that didn't make it; and I've seen every piece of driftwood and debris for kilometres of beach covered in the ones that did. Diabrotica sp. beetles also seem to have a propensity for riding the wind. Seldom is it that I can sit on the beach after a swim and don't find at least one Diabrotica sp. nearby. Other species may congregate on beaches too, not brought there by the lake breeze, but instead to feast on the concentrations of Stable Flies. In late summer and autumn, for example, migratory dragonflies, like Common Green Darner (Anax junius), take advantage of the abundance at Long Point. Let them eat their fill I say. By that I mean the dragonflies, not the stable flies!