Kāruhiruhi and kawau paka nesting on the lower lake

With the upcoming lower lake restoration project at ZEALANDIA (the Sanctuary to Sea project), conservation staff thought it would be good to get a baseline on shag nesting so we could measure any effect that the programme might have. We have therefore started monthly counts of shag nests around the lower lake – something last done in the 2015/16 season.

The October count gave us a total of 44 nests, an increase on our previous highest count of 40. Species type slightly favours kāruhiruhi (pied shags) with 24 nests, the remainder being kawau paka (little shags). Comparing back to the October 2015 count we had 39 nests split 21 kāruhiruhi/18 kawau paka so the ratio has remained much the same.

The kāruhiruhi nest predominantly in the large macrocarpa tree on the west side, and on the fallen trees by the pontoon. The kawau paka nest in the trees between the Shag lookout on Lake Rd and Alison’s Memorial loop track, with a few in the large macrocarpa and the trees just to the north of it (ask a ZEALANDIA guide to point them out).

Various people have suggested that the increasing number of kāruhiruhi might cause a problem and ‘crowd out’ the kawau paka. Overall nesting numbers show no evidence of this and a recent behaviour is particularly remarkable.

Earlier in the year we had a kāruhiruhi nesting and successfully fledging two chicks from a nest below the Lake Road chain link fence. This was the first time we had seen a shag of any kind nesting that far north on the lake.

Subsequently three further pairs have built nests in the same location and all three appear to be sitting on eggs.

We observed when we did the October nest count that a kawau paka had nested in the same tree as the kāruhiruhi. This weekend we saw that there are now three kawau paka nests in the same tree with possibly a fourth under construction – hardly a case of being ‘crowded out’.

For the best view of the shag nesting colonies, take a ride on our electric boat which runs most weekends, weather dependent.