The first asparagus is up. The greenflies are sucking the life out of the few broad beans plants that survived the gnashers of the garden’s winter visitors. The bowerbirds are brutalising the new growth on the liquidambar, in a jaunty colourised style that makes me think we have a flock of Calamity Janes in the canopy. Spring is here!
But what about the spring birds? I haven’t heard the first koel of the season, but the channel billed cuckoos have squawked their way into our dreams. And in the last week, a new rolling trill in the trees: the olive backed orioles have returned. We rarely see them around here, but according to Michael Moorcroft’s “Birds of Australia” as “common”. The emergent twitcher in me sighs.
I met a charming French skin specialist once, and asked her why she moved to Sydney. “We have melanoma in France of course” she said “But really, if you are interested in skin cancer, Australia is the place to be”.
On the other hand, if you long for the sight of that first feathered visitor arriving from a epic transcontinental journey, you’re better off in the Northern hemisphere. All the ocean in the southern half of the globe, moderating seasonal temperatures; barriers of forest and ocean; a less icy past; uncertain rainfall and an often arid climate; and (somewhat unconvincingly) weirdly, lots of “V” shaped continents; all reasons I’ve come across to explain why we have so few migrating birds around here (Someille et al 2013; Dingle 2008).
Back home, two thirds of my French oncologist’s local birdlife would be part time residents. But in Sydney, it’s maybe one in five. In the outback there are nomads, roaming around trying to find things to eat in an arid landscape, but there are hardly any regular migrants at all.
Tasmanian silvereye mid-migration, Zosterops lateralis lateralis
What we do have lots of in Australia are “partial migrants”. Somewhere between a third and a half of bird species have some sedentary individuals while others take off in the colder weather (Chan, 2001). Most silvereyes, for instance, stay put, but many Tassie birds – chunky numbers with chestnut sides, like the one above – fly across the Bass Strait in winter, possibly island-hopping as they make their way to Victoria, NSW and Queensland. On my way to work the other day, I was was befuddled by the strange appearance of a crew of migrants – on their way home, perhaps – milling around happily in the company a bunch of plain-brand silvereyes.
Hard working bird lovers have been tagging silvereyes for 30 years (Chan, 2001), so we know what these guys are up to. But in general, partial migrants are tricky customers – figuring which of the identical birds you see are interstate visitor and which are locals is mostly pretty hard to do.
After reading a bit about research on bird internal navigation systems, I’m starting to think this kind of deviousness may be payback.
One set of experiments involved keeping captive birds and observing what corner of their cage they batter themselves against, driven by migration-restlessness or Zugunruhe (one of those cool German words for which there is no English equivalent). Researchers messed with the heads of these captive birds, using mirrors to shift the apparent direction of the sun so they could see what new quadrant of their cage they try to escape through. Other experiments placed caged birds inside a magnetic coil to warp their sense of direction – a research activity truly worth of evil genius from X-Men. Although I do find the thought of a bunch of 1940s songbirds flooding into a planetarium – another early experiment – quite charming (Burton 1992).
If you do see a trans-continental migrant in Australia, it will probably be a shorebird. About 35 beach loving species migrate here (Dingle, 2008). On a paddle up Mooney Mooney Creek last weekend, I was really happy to see one of them: an eastern curlew, its absurdly long beak mucky after joyously feasting on the mud-flat crabs off Spectacle Island. Flying from Siberia will take it out of you. Between the bloody photographers, the houseboats and the jet skiiers, it’s not hard to see why these guys are classed as critically endangered around here.
References
Burton, Robert (1992) Bird Migration, London: Aurum Press
Chan, Ken (2001) “Partial migration in Australian landbirds: a review” Emu, 2001, 101, 281–292
Dingle, Hugh (2008) “Bird migration in the southern hemisphere:
a review comparing continents” Emu (108), 341-59
Somveille M, Manica A, Butchart SHM, Rodrigues ASL (2013) Mapping Global Diversity Patterns for Migratory Birds. PLoS ONE 8(8): e70907. doi:10.1371/
journal.pone.0070907
