Long Point Bird Observatory 2016 Year End Report

The first Barred Owl (Strix varia) ever banded at Long Point Bird Observatory was captured in 2016.

Photo: Terren (Wikimedia Commons)

In 2016 Long Point Bird Observatory (LPBO), the oldest bird observatory in the western hemisphere, completed its 58th migration monitoring season. LBPO banded 44,612 birds last year. Additionally 5,419 recaptures of previously banded birds were processed. The first Barred Owl ever banded at LPBO was captured during the fall season. Other notable banding records included the eighth ever Broad-winged Hawk (the first since 2006), the fourth ever Painted Bunting and record high banding totals for:

· Cliff Swallow, 22 (previous record was 13 in 1982);
· Oregon Junco, three (single birds banded in six previous years)
· Red-eyed Vireo, 496 (previous record was 490 in 2012);
· Summer Tanager, four (tied with 2009);
· Tufted Titmouse, five (previous record was four in 2005);
· Warbling Vireo, 162 (previous record was 143 in 2014); and
· Yellow Palm Warbler, six (tied with 2005).

Despite these highlights, LPBO banded the fewest birds since 2004. Last year, LPBO banded 15.5% (4,498 individuals) fewer birds than the previous 10-year average. The story was no better for the number of species and forms, with 2016 again being the lowest total since 2004. The 141 species and forms captured in 2016 was about 10% (16 species) below the previous 10-year average.

The complete 2016 Year End Report can be found here.

Ontario Tiger Beetles

Ghost Tiger Beetle (Cicindela lepida)

Photo: Canadian Biodiversity Information Facility

The Norfolk Sandplain, my home turf, hosts 10 of Ontario's 14 tiger beetle (family Cicindelidae) species. Any outing during the warm months means an encounter with at least a few of these fascinating and beautiful beetles; whether it's a concentrated search for one of the province's rarest species, the Ghost Tiger Beetle (Cicindela lepida), or a pleasant afternoon on the Lake Erie shore swimming and watching Beach (Cicindela hirticollis) and Bronzed (Cicindela repanda) Tiger Beetles stalking the sand, Cicindelids will be there. To help me keep my tiger beetles straight, I've put together a simple field guide that will aid in the identification of all Ontario species. The pictures come from the Canadian Biodiversity Information Facility.

Naturescape: Blue Dasher

An immature Blue Dasher (Pachydiplax longipennis).

Photo: Mark Conboy

The False Allure of Garlic Mustard

The West Virginia White (Pieris virginiensis) is highly localized in Ontario. This one is nectaring on a non-native mustard. The presence of non-native mustards is partly responsible for the decline of the this woodland butterfly across much of its range.

Photo: Randy L. Emmitt (Wikimedia Commons)

Eastern Onatrio's Frontenac Arch is home to a wide variety of species at risk, including an unassuming woodland butterfly, the West Virginia White (Pieris virginiensis). It's a butterfly that's notable for a number of reasons: it's truly sylvatic, whereas almost all other Ontario butterflies are found in open habitats; it's restricted to only a handful locations in the province, and it has apparently disappeared from many of those sites in recent years; and perhaps most importantly, it has a taste for mustards (family Brassicaceae). It's a combination of all three of these things that has earned the West Virginia White the designation of a species of special concern in Ontario.

I have fond memories of living among West Virginia Whites, which I could find flying in May only a short bike ride away from my cabin on Opinicon Lake. My favourite West Virginia White colony, was found under a forest canopy composed of some thirty species of trees, where salamanders seemed to reside under every fallen log, and spring wildflowers bloomed in ridiculous profusion. Among the abundant wildflowers were two toothworts: Cut-leaved (Cardamine concatenata) and  Two-leaved (Cardamine diphylla), and it was upon these forest floor mustards that my West Virginia Whites fed. It's been several years since I last had the opportunity to visit my old colony, but I wonder with genuine concern how those rare butterflies are fairing.

In the past, the most pressing threat to West Virginia White populations throughout Ontario would have been loss or fragmentation of the mature forest habitat they and the toothworts require. Happily, my colony was safe from any kind of forestry, tucked away as it was on a large swath of protected land. The there was something else to worry about back then, in those heady days with my butterfly colony, and it's a worry that persists today: the insidious Garlic Mustard (Alliaria petiolata).

Garlic Mustard was intentionally introduced to North American from Europe as an edible herb during the mid 1800's. It has since expanded across the Great Lakes region and throughout much of the northeastern United States. Once established, it spreads like wildfire, choking out native vegetation and turning large areas of forest understory into Garlic Mustard monocultures. It's a terribly invasive species, more deserving of the appellation "weed" than almost any other woodland plant.

Just like the toothworts, Garlic Mustard is a member of the family Brassicaceae, the mustards. The mustard family includes such human favorites such as Broccoli, Cabbage and Cauliflower (Brassica oleracea), Turnip (Brassica rapa), Canola (Brassica napus), Common Radish (Raphanus sativus) and Horseradish (Armoracia rusticana). Many of these garden species are popular foodplants for introduced Cabbage White (Pieris rapae) caterpillars, but for West Virginia Whites the options are fewer because not many mustards grow in its dark forest habitat. The toothworts do and, unfortunately, so does Garlic Mustard. Indeed, I've spent more time than I care to recall pulling up Garlic Mustard in my woodlot. It's an annual chore, but it works to keep the forest floor more or less free of the nefarious weed. I fear however, that no one has been pulling Garlic Mustard at the old colony I used to visit years ago, and that may be cause for concern.

Garlic Mustard can out-compete the native toothworts for sunlight and soil nutrients, effectively eliminating them from the forest floor, leaving West Virginia Whites without their native foodplant. Interestingly, the butterflies will switch to using Garlic Mustard as a foodplant in the absence of toothworts, and may even prefer Garlic Mustard over toothworts. At first glance it seems like a fair trade off: replace one mustard with another and carry on. I mean, wouldn't stand to reason that the spread of Garlic Mustard would lead to a flourishing of West Virginia Whites, just as the planting of Crown Vetch (Securigera varia) along roadsides throughout southern Ontario has led to a drastic range expansion of Wild Indigo Duskywings (Erynnis baptisiae). In the case of the duskywing, which was once restricted to a small portion of southern Ontario, it has recently taken up the non-native vetch as a new larval foodplant and expanding its range as a consequence of this new widely available resource. In western North America, the naturalization of non-native Fennel (Foeniculum vulgare) has allowed Anise Swallowtails (Papilio zelicaon) to produce produce two flights every year, when previously it produced only one. This shift from unvoltinism to multivoltinism in the swallowtail was assisted by the tremendous abundance of Fennel which augmented the supply of natural carrot family (Apiaceae) foodplants. In strong contrast, however, the abundance of Garlic Mustard has actually had a negative effect on West Virginia Whites.

Lab experiments and field observations in the American portion of the West Virginia White's range have shown that caterpillars which feed on Garlic Mustard never reach maturity, usually dying after several days. Garlic Mustard, though attractive as an ovipositing site to adult females, is actually a death sentence to any caterpillar unlucky enough to hatch there. The Garlic Mustard's chemical defenses and a suite of growth inhibitors in the plants kill all caterpillars by the time they reach their second instar. Or at least that's the case in most populations. In at least one Massachusetts  population, however, caterpillars are able to survive until the pupal stage by feeding on Garlic Mustard alone. Though the caterpillars took longer to pupate and were a third smaller than caterpillars that grew up on toothworts, they did survive. Perhaps other populations of West Virginia Whites may also be able to adapt to use Garlic Mustard.

There may be some hope for West Virginia Whites if other population can shift to using Garlic Mustard successfully. But that's not likely to happen soon enough to stop the decline of this species all across its range. Evolution is a long and often risky road, after all. It seems that combating Garlic Mustard where it has become established and keeping it from spreading into pristine woodlands in the first place is the best defense we can give West Virginia Whites. So I keep pulling and spraying Garlic Mustard in my woods and I keep hoping that the old colony of mine is still flourishing under those big trees half a province away, and not just in my memories.

Naturescape: Grape Plume Moth

Grape Plume Moth (Geina periscelidactylus).

Photo: Mark Conboy

Naturescape: Beautiful Wood-Nymph

Two Beautiful Wood-Nymphs (Eudryas grata) put on a convincing disguise as bird droppings while they rest with impunity out in the open on a River Grape (Vitis riparia).

Photo: Mark Conboy

Naturescape: Edward's Hairstreak

An Edward's Hairstreak (Satyrium edwardsii) nectaring on a Butterflyweed (Asclepias tuberosa).

Photo: Mark Conboy

Naturescape: Zebra Swallowtail

This immaculate Zebra Swallowtail (Eurytides marcellus) was found at the Tip of Long Point, Ontario in June 2016. It was the first record of this species at Long Point since the 1970's (according to the Ontario Butterfly Atlas) and the first one in all of Ontario since 2012.

Photo: Mark Conboy

Naturescape: Darth Vader Fly

I've always called this massive horse fly the Darth Vader Fly, for obvious reasons. Measuring up to 3 cm long, Tabanus atratus is a very large for a fly, especially one that has razor-sharp mouth parts. I've never been bitten by one, but I'm sure it hurts like crazy!

Photo: Mark Conboy

Naturescape: Brachyleptura rubrica

Brachyleptura rubrica, like dozens of other longhorn beetle species, are important pollinators. This one is covered in Spotted Water Hemlock (Cicuta maculata) pollen.

Photo: Mark Conboy

Butterfly Oasis

A Great Eggfly (Hypolimnas bolina), Owl Butterflies (Caligo sp.) and a Red Mormon (Papilio rumanzovia) feed on fruit at the Niagara Butterfly Conservatory

Photo: Mark Conboy

 

In the dead of a Canadian winter, the naturalist's heart longs for butterflies. It's still at least a month and half before the first Canadian butterflies can be expected on the wing, but there is one oasis of butterfly activity in southern Ontario, the Niagara Butterfly Conservatory. Here's a photo essay of some of the species that were on the wing during a visit I made in early February.

 

Grey Cracker (Hamadryas februa)

Photo: Mark Conboy

 

 

Zebra Longwing (Heliconius charithonia)

Photo: Mark Conboy

  

Great Eggfly (Hypolimnas bolina)

Photo: Mark Conboy

 

Great Eggfly (Hypolimnas bolina)

Photo: Mark Conboy

 

 

Red Mormon (Papilio rumanzovia)

Photo: Mark Conboy

 

Red Mormon (Papilio rumanzovia)

Photo: Mark Conboy

 

Tiger Longwing (Heliconius hecale)

Photo: Mark Conboy

 

Paper Kite (Idea leuconoe)

Photo: Mark Conboy

 

Plain Tiger (Danaus chrysippus)

Photo: Mark Conboy

 

Red Postman (Heliconius erato)

Photo: Mark Conboy

 

Julia (Dryas julia)

Photo: Mark Conboy

 

Blue Wave (Myscelia cyaniris)

Photo: Mark Conboy

 

Peleides Blue Morpho (Morpho peleides)

Photo: Mark Conboy

 

Peleides Blue Morpho (Morpho peleides)

Photo: Mark Conboy

 

Illioneus Owl Butterfly (Caligo illioneus)

Photo: Mark Conboy

 

Mexican Cycadian (Eumaeus toxea)

Photo: Mark Conboy

 

Montezuma's Cattleheart (Parides montezuma)

Photo: Mark Conboy

 

Isabella's Longwing (Eueides isabella)

Photo: Mark Conboy

 

Common Mormon (Papilio polytes)

Photo: Mark Conboy

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.

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!

BioBrevia: Hope for the Old Fashion Field Naturalist

Illustration: Philip Henry Gosse 

This brief article from Science, Explosion in new Dragonfly Species Results in Animals Named after Gorillas, Pink Floyd, and the accompanying presentation, are great inspiration for would-be naturalist-explorers. A small team recently described 60 new species of dragonflies and damselflies from west and central Africa. All of these species were recognized in the field before they were diagnosed using genetics in the lab, demonstrating that an abundance of new species still await discovery the old fashioned way, by simply getting out in the field and knowing your stuff. The actual journal article in which the new species are described is available from Odonatologica.

Columbine Graveyards

Serpentine Columbine (Aquilegia eximia)

Photo: David A. Hofmann (Creative Commons)

The oak savannah and Chamise (Adenostoma fasciculatum) chaparral of California's North Coast Ranges, are interrupted here and there by a unique and altogether surprising floral community: plants that grow on poison. In this case, the poison is serpentine, rocks that are so rich in magnesium and iron that they, and their associated soils, are toxic to most plants. Most, but not all.

There are some plants that can grow on serpentine deposits and many of those are rare and endemic, not to mention highly adapted, making serpentine flora one of a most intriguing element in California's generous biological endowment. Among the most exquisite serpentine plants is Serpentine Columbine (Aquilegia eximia), which displays large red and yellow flowers to attract the attention of pollinators. In addition to pollinators, Serpentine Columbine attracts great many other insects, but for a totally different reason.

Plants attract animals to help them with all kinds of tasks; the two most obvious, of course, are pollination and seed dispersal. Pollinators are attracted by scents and visually stimulating flowers. Take the elaborate deceptions of the Fly Orchid (Ophyrys insectifera), which wafts bee pheromone-like scents from its bee-shaped flowers. Real bees come not in search of pollen or nectar, as they might at a more conventional flower, but instead they come to mate with the lookalike blossom, in the process getting coated in pollen. The bees pollinate the next orchid they visit in another misguided hope for sex.

Some plants are entirely dependent on animals for dispersing their seeds. In the Rocky Mountains, Clark's Nutcrackers (Nucifraga columbiana) are the near-exclusive disperser of Whitebark Pine (Pinus albicaulis) seeds, transporting them great distances and planting them in suitable habitats.

Examples of animal pollinators and seed dispersers are virtually limitless, but there are lots of other reasons for plants to attract animals. Sometimes it's to eat them. Venus's Flytrap (Dionaea muscipula), is probably the most dramatic of the so-called carnivorous plants, capturing and later digesting insects and even small frogs between snap tap-like leaves. Even the ubiquitous Field Thistle (Cirsium discolor) may capture insects using sticky secretions on its flowers; those same secretions act as digestive enzymes, digesting stuck insects and providing an unusual food source, at least among thistles species.

Other plants feed off animals in more passive ways. The impressive Queen of the Andes (Puya raimondii) offers paramo birds a safe haven among its hooked leaves in exchange for the highly nutritious droppings the birds leave behind. As an added benefit to the plant, a bird occassionally gets hooked among the thorny leaves, dying and providing an even richer source of nutrients for the giant bromeliad.

Some plants attract animals to help them battle damaging herbivores. Azteca ants are provided with living spaces in Ceropia trees and are fed from extrafloral necataries, in exchange for doing battle against caterpillars and other damaging herbivores. Providing shelter and nectar is a pretty conventional way of attracting helpful predators, but there are a few plants, including the Serpentine Columbine, that attract protective insects in a completely different way, and that's by essentially becoming arthropod graveyards.

Serpentine Columbine stems are covered in glandular hair-like trichomes, making them very sticky. So sticky, that they trap insects by the dozens. These trapped insects in turn attract predatory arthropods. The predators come to dispatch trapped living insects or to feed on the corpses of those that have already died. The predators are called upon to primarily combat caterpillars of the Darker Spotted Straw Moth (Heliothis phloxiphaga), which feed on the leaves, buds and even the flowers. The columbine's glandular hairs seem to be of little use in combating this caterpillar, so the plants rally Checker-rimmed Bugs (Pselliopus spinicollis), other true bugs (Order Hemiptera) and even the occasional crab spider (Mecaphesa spp), to help stavse off assault. Between meals of caterpillar, these predators feast on the stuck insects. This buffet style call to arms seems to be effective, columbines with more stuck insects (thus more helpful predators) usually experience greater reproductive success.

The insects that Serpentine Columbines capture aren't, for the most part, pollinators or herbivores that accidentally become stuck, but instead appear to be actively attracted by the plants through some kind of chemical signal. What exactly that signal is remains unclear, but it appears that Serpentine Columbine is the only plant so far known to actively attract insects in this way. Yet another remarkable find from the fascinating serpentine deposits of northern California!

Oropendola Economics

Chestnut-headed Oropendola (Psarocolius wagleri)

Illustration: Source Unknown 

I've said it once and I'll say it again: never underestimate blackbirds. Blackbirds are perhaps the most underrated songbirds; they are too often discounted, brushed off, or simply ignored. When they do attract attention its usually for all the wrong reasons. They're maligned as agricultural pests, though many species are more beneficial to farmers for eating insects, than they are destructive in consuming crops. They're derided as ugly, even though a great many species are beautifully coloured - orioles are blackbirds, let us not forget. They're considered noisy, clamorous and obnoxious, when in truth many species have remarkably intriguing, if not utterly beautiful, songs; consider a meadowlark singing on a warm spring day. But such nearsightedness is a fool's understanding. The truth is we must never take the blackbirds for granted, we must never underestimate them, especially the tropical ones!

Among the most conspicuous, and certainly the most charismatic tropical blackbirds are the oropendolas. They're big, badass, flashy (as far as blackbirds go), and their vocalizations are stranger than Norwegian prog rock. Their nests, which take weeks to construct, are incredible feats of engineering: pendulous, intricately woven, and arranged in conspicuous colonies hanging above the forest canopy from the limbs of a enormous emergent, or in an isolated farmland tree. Oropendolas are full of surprises. For example, they've been seen catching hummingbirds. But the most fascinating aspect of oropendola natural history may be their reported relationships with wasps, bot flies and cowbirds.

In Panama, some Chestnut-headed Oropendola (Psarocolius wagleri) colonies are built in trees that are also home to colonies of highly aggressive predatory wasps. The wasps unwittingly assist the oropendolas in two ways. First, they keep most would-be predators at bay; after all who wants to mess with a bunch of ornery flying hypodermic needles? Second, they keep the colony more or less free of parasitic Philornis bot flies. Wasps are hunters after all, using their venomous stings to defend their colonies and subdue their prey. Philornis bot flies are common parasites of neotropical birds. In oropendola colonies Philornis lay their eggs on nestlings, when the eggs hatch the larvae burrow beneath the bird's skin and begin syphoning off the precious resources that the baby birds themselves need to grow. When those neighbourly vespids are present, nestling oropendolas seem to suffer fewer instances of parasitism, but in colonies depauperate of wasps, nestlings can suffer from relentless bot fly parasitism. Infestations can actually be so intense that they can cause widespread nestling mortality.

Enter the Giant Cowbird (Molothrus oryzivorus). Giant Cowbirds, like our familiar North American Brown-headed Cowbirds (Molothrus ater) are brood parasites. They don't build their own nests and raise their own kids, rather they seek out the nests of other species and  foist all parenting responsibilities upon them. Brood parasitism has evolved several times among different families of birds. Cowbirds and cuckoos are perhaps the most famous example, but numerous other birds do it too: some finches, honeyguides, and even ducks. Some brood parasites are fairly choosy, laying their eggs in the nests of a specific host species. Giant Cowbirds, for example, mostly parasitize oropendolas and the closely related caciques, though orioles can make suitable surrogates in a pinch.

Being parasitized doesn't come without consequences. Usually, a host will experience reduced success in raising their own offspring if they also have to raise a parasite's chick. This can be for a number of reasons, like host egg ejection by female cowbirds, or accelerated growth rates of cowbird chicks compared to host chicks. In some cases, hosts will simply abandon their nest and begin the breeding process again. Yellow Warblers (Setophaga petechia) will construct a brand new nest directly on top of their old one, smothering not only the cowbird's eggs but their own as well. Because of the risk that parasitism will result in reduced nesting success, oropendolas normally aggressively defended their nests from Giant Cowbirds. When a cowbird approaches a nest, the colony may irrupt in excitement and the nest owners will do their best to see the interloper off. But at some Panamanian oropendola colonies, astoundingly, Giant Cowbirds are apparently allowed to parasitize the nests! Why?

Colonies where parasitism is reportedly allowed are those which don't have aggressive wasp neighbours to help keep the vicinity clear of bot flies. Remember, that bot fly infestations are most severe when wasps are absent. But Giant Cowbird nestlings in their constant hunger, appear to actually remove bot fly larvae from their oropendola nest mates. They pick the larvae right off their fellow nestlings. In colonies with high a incidence of bot fly infection cowbirds may actually help improve the chances of oropendola survival. In colonies with few bot flies (because of more wasps) cowbirds are only a detriment, so they are vanquished.

This curious piece of natural history, the association between oropendolas, wasps, bot flies and cowbirds has been cited time and again in the scientific and popular literature. It shows up in print frequently enough to give the impression that this complex set of avian-insect interactions is common and widespread; in actuality, it has only been documented in one study dating back to the 1960's. It seems to have never been observed again in Panama, where it was originally described, or anywhere else in Latin America. It's not as though no work has been done on oropendolas since the 1960's. In fact, some studies have even looked at other aspects of Giant Cowbird interactions with other oropendola and cacique species, but have not reported the same types of interactions. Certain authorities on blackbirds have even called into question the validity of the work itself. Certainly, more study is needed. Hopefully, further work in the neotropics will rediscover the oropendola-cowbird mutualism, but if not, there are doubtless even more complex and intricate ecological interactions to be found, and I eagerly await their discoveries.

Non-Newtonian Harvestmen

Harvestman (though not the Mitostoma chrysomelas of this post)

Photo: Dschwen (Wikimedia Commons) 

One of the most common cases of mistaken identity in the natural world is the colloquial classification of harvestmen as spiders. Fact: harvestmen are not spiders at all; arachnids, yes, but spiders, no. Harvestmen are a group unto themselves (order Opiliones), and are far more closely related to scorpions and pseudoscorpions than to spiders (despite their superficial resemblance). However, this kind of taxonomic milieu is nothing more than pedantic babble if you happen to be a springtail cornered by a harvestmen in the leaf litter. You see, to the average springtail, a harvestmen is death on stilts. Sticky death on silts.

Some interesting research has used high-speed videos to capture the harvestman Mitostoma chrysomelas hunting springtails. Mitostoma ensnare their extremely fast-moving prey using sticky setae (hair-like structures) on their pedipalps. Each setae bears a droplet of super sticky glue that has just the right chemistry and physics for capturing springtails. It has long been suspected that these droplets were used by harvestmen to hunt, but this study is the first to actually document it.

Springtails are one of those groups of hexapods that go more or less unseen. Most species are tiny, like the snowfleas (Hypogastrura nivicola) you may come across on a warm winter's day. Some of the larger southern hemisphere springtails approach a centimetre in length, but they, like their diminutive cousins usually remain out of sight, in the soil and leaf litter. They have some marvellous adaptations, not the least of which is the ability to launch themselves extraordinary distances using their spring-like furcula (the springtails' eponymous jumping organ). Most springtails can also shed liquids like a rubber raincoat, an important adaptation for living in wet soils. Both of these features, it would seem, are just the sort of adaptations that would keep springtails safe from predators like harvestmen, but that's not the case when it comes to Mitostoma.

 

Mitostoma glue is one liquid that springtails can't shed. Rather, the glue can stick to springtails without any trouble at all, establishing a firm hold that becomes ever more firm the longer and harder a springtail struggles. A springtail, with it's power-packed furcula, can put up a good fight, but for all the effort it exerts, the springtail only ensures itself a more certain doom. That's because Mitostoma glue becomes more viscous - it gets thicker, becoming a more effective trap - the faster it is pulled away from the setae by struggling prey. The pressure exerted by the distressed springtail causes the harvestman's glue to, in a sense, solidify. Liquids that posses this property are called non-Newtonian fluids: their viscosity changes when forces are applied to them. Some non-Newtonian fluids become more viscous, like when you stir gravy, while other liquids become less viscous, like when you shake ketchup out of a bottle. In both of these cases, the application of pressure to the fluid changes its viscosity. (Newtonian fluids, by the way, typically don't respond to pressure in these ways; think about splashing your feet in a puddle - there's no change in the water's viscosity.)

The non-Newtonian properties of Mitostoma glue make escape for springtails a highly unlikely outcome, should they be captured in the menacing pedipalps of a harvestman. It's all part of the incredible predator-prey relationships going on at the macro level around us all the time. I have often told students that if they are interested in predator-prey interactions they needn't spend fruitless weeks and months following Polar Bears (Ursus maritimus) on ice flows to see a rare dispatching of a Ringed Seal (Pusa hispida), or trek over endless kilometres of mountain wilderness in hopes of seeing a Cougar (Puma concolor) take a Bighorn Sheep (Ovis canadensis), but rather to begin by watching the countless invertebrate battles for life and death that surround them in their own backyards. Though small, the non-Newtonian harvestmen prove that the macro world is well worth watching.