Migratory patterns

Greetings I’ve been a member of Birding Aus for a couple of years, but rarely posted anything, so this is in some respects introductory. I’m a research scientist by training, commercial scientist by vocation, meaning that my career was primarily in the commercial domain of companies like Bunge, Cadbury and the sugar industry. I semi-retired 10 years ago and moved about 6 years ago to Swanwick, near Coles Bay on Tassie’s beautiful East Coast. I’d previously lived in East Gippsland, Melbourne, Canberra, Daylesford/Ballarat, Brisbane and Mackay (but there is no migratory pattern in that). I’ve birded over a wide range in Australia, including many of the must-visit spots like Bowra, Winton, Mt Isa, Karumba, Eungella, Barrier Reef islands, Cairns/Atherton Tableland, Gluepot, Cocoparra, most of Tas including Eaglehawk Neck pelagics etc. I’m not a lister, but have some enthusiasm for non-invasive wildlife photography, including habitats. The Swan River at Swanwick forms the lower extreme of a Ramsar wetland known generally as Moulting lagoon. Since moving here I’ve become very aware of the apparent randomness of bird migrations, with many of my observations not reproduced from year to year, or involving few or solitary birds. A few examples: Grey-tailed tattler: solitary bird turned up in late spring, at a place called River and Rocks, on the Swan River estuary 1km upstream from Swanwick township, for 3 successive years from 2009-2011; arriving variously from late October through early December, and leaving from late February through mid-April. Has not been seen since. Latham’s Snipe: Starting with a solitary bird in spring 2010 and reaching a maximum of 3 birds in spring 2013, these birds occupied a small damp grassy area adjacent the Swanwick golf course only until mid summer at the latest. After some interference with this tiny habitat, they did not return in 2014. Banded stilt: On one occasion only, in autumn (20/4/14), a migratory flock of about 50 birds turned up on a shallow tidal flat upstream from Swanwick in the Swan River. They stayed tightly packed, just resting, then flew on overnight or early the next morning. I have not seen them since in this location, but I have a vague recollection of someone (a non-birder) seeing something similar in autumn this year, without precisely identifying the species. Hoary-headed grebe: a large flock (about 250 birds) arrived in late July 2014. Initially very flighty, they settled into several (3-5) flocks dispersed over a stretch of Swan River 1-2 Km upstream from Swanwick, where they stayed until mid-September. I had not seen in earlier years, and it has not happened this year. Bar-tailed godwit: A small flock turn up on the Pelican roost (a tidal sandbank opposite River and Rocks) every year, usually in October and staying until March/April. Numbering 12-15 birds in 2009-11, only 7 arrived last year, tending to support a pattern of decline seen more generally. I have images of most of these if anyone wants them. There are other examples I could give, but suffice to say I’m reaching an obvious conclusion; that Tassie is at the migratory extreme range for a number of species, hence the apparently random events. On the other hand, a number of land species have patterns much more consistent, for example, some altitudinal migrants arrive in the coastal fringe in June/July each year and depart to higher altitude to breed in late winter/early spring (eg Crescent honeyeaters, Golden whistlers, Bassian thrushes). Others arrive in this area in late winter/early spring to breed through the summer months (Spotted Pardelotes turned up on 19/8 (normal), a Pallid cuckoo was heard on 22/8 (early by 2 weeks), but not heard since, and a Fantail Cuckoo was heard on 25/8 (at least a week later than last year). It has been the coldest winter for some years down here , and one could speculate on the relative influence of climate change, local or regional short-term climate variations, and increasing or decreasing day length as a migratory trigger, but they are discussions for another day, and need a lot more data than I can offer. Regards Graeme Bullock Email: gebullock08@bigpond.com> gebullock08@bigpond.com Skype: graeme_bullock