On a sunny but cool morning a full complement of members and guests joined me on the MV Darter for this now annual trip to view the darter and cormorant nesting. This year's trip had added significance as it was the first one since the complete clearing of the trees on the northern bank in May 2008.
As this boat is much faster we had time to visit the SE corner of East Basin first, including the construction works around the former Kingston Boat Harbour and up Jerrabomberra Creek for a few hundred metres. We soon saw numbers of Australasian Darter, mostly loafing or drying their wings along the newly built wall on the entrance to the creek, totalling about 30 and all in female, or more likely, immature/juvenile plumage. Also resting along here were about 30 each of Masked Lapwing and Silver Gull. On entering the creek proper we were immediately struck by the large numbers of birds on the water, which turned out to be at least 150 Pacific Black Duck and about 70 Black Swan, complete with some half-grown cygnets and further up the creek a bird on quite an open nest close to the bank.
The twin questions of where were all the male darters and had the clearing made a difference to the extent of nesting were soon answered when we moved up the Molonglo Reach. There were many Australasian Darter nests, as usual spread along the southern bank singly or in small groups. At least 10 birds, often males, were sitting tight on nests. Also seen were a number of nests with nearly or recently fledged chicks, identified by their yellowish colour when sitting close together on a nest or from their clumsy behaviour when still close to one. Altogether about 60 birds were seen on this stretch, about 1/3 males and 1/3 young birds. Interestingly no downy chicks were seen, indicating a distinct pattern with an apparently major breeding event some months back followed by a recent new commencement. Given that the last 6 weeks have been very dry the trigger for this new batch of nests is unclear. There were no nests observed on the now cleared northern bank, though Chris Davey tells me there were at least a couple of nests in bare trees here earlier in the season.
Where the reach opens up much wider about 0.5 km west of the first bridge, there were five newly built or still being built, close together Great Cormorant nests with a dozen birds resplendent in their very dark breeding plumage with a very obvious yellow and white cheek, a white flank patch and a clearly obvious crest. Just past this area was a single Little Pied Cormorant wedged between several darter nests, the only one of this species seen for the morning. About 10 Little Black Cormorants were seen during the morning, but with no evidence of any breeding behaviour. Also seen was an Eastern Great Egret, identified by its neck being much longer than its body when it obligingly settled on the bank close to the boat.
So the answer to the question of whether the clearing of the trees on the northern bank had affected the extent of breeding is clearly no, at least in respect of this season, for the Australasian Darter and the Great Cormorant. The numbers of darters counted is equal to or slightly in excess of those seen on the same day last year, before the northern bank was cleared, and the breeding season would seem to be at least similar to the very successful one last year, particularly if the new batch is successful too (from previous trips the species is known to still have chicks in the nest in late May). In addition, Jim, our skipper has noticed one or two spots around the lake where he has not seen darters nesting previously, eg West Basin along the shore parallel with Lawson Crescent near the old hospice and near the golf course water pump pick up along Yarramundi Reach. Numbers of nesting Great Cormorant were slightly higher than last year, but lower than the maximum numbers seen in April 2007, so too don’t appear to be affected, though the very late start to the breeding compared with previously may be significant.
The extent of breeding of Little Pied and Little Black Cormorants was already very low in 2007 and 2008, with the former in particular now favouring a nest site just west of the mouth of Sullivan’s Creek as reported from the COG boat trip at the end of March 2008. The significant nesting there again this year has already been noted on the COG chat line and on 28 February Rod McKay paddled down there and saw lots of activity with birds carrying nesting material, mating and feeding dependent young. He estimated there were at least 150 Little Black Cormorants there with 45 nests (very similar numbers to last year), a lone Little Pied Cormorant nest, and a lone Great Cormorant nest (with two birds in attendance), but only one Australasian Darter nest along the whole eastern side of the peninsula.
As for this time last year the river was very quiet in respect of other water birds, with few ducks and surprisingly not even a Coot seen. Land birds too were quiet though the total of 38 species seen was just below average based on previous years.
The 16 participants thoroughly enjoyed themselves as I did even though it was my tenth trip in six years. I look forward to leading my next trip; every time you go up the reach there seems to be something different.
— Jack Holland