Sunday, May 1, 2016

I'm usually the one on dog duty in the morning.  My walking route takes me around a nearby elementary school.  And at least once a year, I've spotted one or two killdeer (I usually hear them before I see them) strolling through the schoolyard on a spring morning.  I used to think that they somehow had gotten lost - they *are* shorebirds, after all - but according to

"Look for Killdeer on open ground with low vegetation (or no vegetation at all), including lawns, golf courses, driveways, parking lots, and gravel-covered roofs, as well as pastures, fields, sandbars and mudflats. This species is one of the least water-associated of all shorebirds."

When I was elementary school age, I had learned from a nature documentary that the killdeer would famously hobble around with what seemed to be a broken wing as a way to distract predators from a clutch of eggs at the nest site.  The killdeer then become a minor character in a story I wrote for Language Arts, a story that became a source of pride when my grade 7 teacher said some encouraging words regarding the maturity of the piece in front of the entire class.  That was probably why I still write about birds today.  Maybe there's a child at this school who has also seen this bird and has written it into a story of his or her own.

Friday, January 1, 2016

HNY 2016

We got to Boundary Bay just in time to catch the sun rise this morning at 8am. While not as cold as last year, it was still below freezing. Bird activity was minimal compared with last year, with a few low flyby's by hawks from behind so that our only photos were tail shots.
Cooper's hawk

Northern flicker.  A common woodpecker in residential areas of the city.

Saw-whet owl
Owls are always the highlight for me, and we would've missed this one down in the thickets if not for some experienced birders lying prostrate aiming their big lenses at this little thing.

Sunday, October 18, 2015

Courting the Hallowe'en pumpkin

Pumpkins aren't the only orange globes in October.  A female Araneus Diadematus in October is typically plump with eggs.  Her large, unwieldy size and cooler metabolism-slowing temperatures makes her move slowly compared to her youthful self mere months earlier.  At this point, she relies on her sticky silk rather than speed to capture prey.

Chomping on a silverfish that mysteriously fell from the sky

I've talked about the life cycle of the cross spider before.  The one most important event I've never documented is how they mate.

Spiders exemplify sexual dimorphism, meaning that males and females have different physical traits, and in many spiders it is so extreme that one could mistakenly conclude that males and females are two different species.  While the two sexes of the giant house spider have roughly the same legspan when mature, the females of A. Diadematus are many times the size of the males, such that the male can (and does) often become a snack for the female.  (Most notorious for this behaviour (and sexual dimorphism) is the black widow)

Recall what I mentioned in the last post about home advantage - this is clearly the case for A. Diadematus as well.  Nearly blind, the male traverses walls, branches, until he finds the threads or webbing of a mature female.  He identifies species and readiness to mate by tasting the threads.  He coaxes the female out by tapping on a thread of the web, but gently and with a different frequency from an insect in distress.  The female approaches the male slowly, but the male must still use caution - the much larger female could at any instant turn on him.  His escape strategy is to tie his anchor line further away, so in a panic, all he has to do is let go to swing to safety.

See the male's pedipalps at the front of his head

The male stores his sperm in his pedipalps, the two leglike appendages at the front of his head.  He needs to reach the female's seminal receptacle at the underside of her abdomen, which incidentally is also the most vulnerable place to be.

A. Diadematus is the largest and most abundant orb (spiral) web weaver in the Lower Mainland, but nearly 100% of the webs you'd ever see are those of females.  Males will start their search for females soon after molting for the last time, and rarely build webs of their own in this last stage (and if they do, they tend to be quite small).  Meanwhile, females will continue building webs well after maturity, as they need to gain the nutrition to build up an egg mass.

A. Diadematus is the most easily observed spider (and dare I say, urban wildlife) in the Lower Mainland and many other parts of North America (I've even seen them in the UK and China)...a great starter spider, if you want to learn more about spiders in general, and the micro-ecosystems that surround us.  Their entire life cycle is at eye level; their existence targets the only insects in these parts that prey on humans (ie. mosquitos); they don't leave behind messy webs; and they live outdoors which reduces the ick factor.  They are one of the last bastions of wilderness that thrive despite humanity.