A few observations, terns, SEQ

To: birding-aus <>
Subject: A few observations, terns, SEQ
From: jilldening <>
Date: Tue, 29 May 2001 13:43:53 +1000
Hello everyone,

I wanted to share a few general observations with you. Some are basic, and not news to experienced people. However, not everyone on birding-aus is experienced. These are things I have noticed when we have been conducting our weekly censuses on the Caloundra sandbanks. Most will be applicable to other similar habitats.

  1. Terns don't share the same habits as migratory shorebirds. The number of terns we see on the sandbanks during daylight hours is greatly less than actually roosts there during the night. Terns fly in from the sea in greater densities at sunset and afterwards. Habits vary between species. I can't tell you what happens after dark, but when we give up, they are still coming in to roost. I am just about to try using night vision glasses, to see if we can pick up movement. I am not sure where the line is drawn between their response to tides and to light. Moonlit nights would probably encourage greater activity than moonless nights.
  2. Both terns and gulls fly in to roost at a greater height during daylight hours than occurs once daylight fades. It is obviously connected with light, or lack thereof, because as soon as light fades, the birds start coming in low over the water. I expect there is more light available (maybe reflected off the water) if they fly low over the water. On very cloudy evenings the birds start flying in low earlier than on clear evenings.
  3. Shorebirds are more active on a dropping tide than on a rising tide. I expect that the food prey is more active near the surface when the sand or mud is recently wet, and as the sand dries out, the prey probably burrow deeper in search of wetter sand. I expect it also has something to do with appetite satisfaction.  So if you're planning to watch shorebirds on feeding banks, you might find them frustratingly inactive on a rising tide.
  4. Small sand plovers love to rest in sand gutters on a rising tide, when they have finished feeding. A bank can appear at first glance to be empty, but scoping can reveal a host of tiny heads scattered singly all over the place. We find this particularly with Red-capped Plovers and Double-banded Plovers at the moment.
  5. In Caloundra we see an increase in shorebird feeding frenzy during the late autumn and winter when soldier crabs are present on the dropping tide. Eastern Curlew, Whimbrel, Bar-tailed Godwit, Grey-tailed Tattler are especially fond of soldier crabs. Terns never feed on sandbanks (should one say never?).
  6. Little Terns have a tendency to rest on banks at the outer edge of large mixed species flocks of terns, rather than in the middle. Individuals will rest among other larger terns, but where they gather in groups, it tends to be at the edge. (This makes it a lot easier to get the detail on flagged Little Terns, whereas a flagged Common Tern can be a trial.)



Jill Dening
Sunshine Coast, Qld
26º 51'  152º 56'
Ph (07) 5494 0994

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