Bird Watch
June/July
2012
Red-billed gull
Larus novaehollandiae scopulinus
Maori names: Tarapunga, akiaki
Red-billed gulls are small,
handsome and abundant. Native
to New Zealand, they are found in
the North, South and Chatham
Islands as well as on subantarctic
islands. They were once thought
to be a subspecies of Australia’s
silver gull, which is very similar in
appearance, but it is now known
they are not especially closely
related. In addition to red bills, they also have red legs and red eye rims. Males and females
look alike, though males are slightly larger than females. Juveniles have dark bills and legs
and easily can be confused with black-billed gulls.
With the exception of a population at Lake Rotorua, they are seldom found more than a few
kilometres inland. They have a wide and varied diet which includes small fish, molluscs,
crustaceans, plankton, marine invertebrates, earthworms, insects, rubbish, and pretty much
anything else they can catch, scavenge or steal. They are known to engage in a behaviour
called kleptoparasitism, which involves harassing other birds into dropping their food.
Between September and December, red-billed gulls form large breeding colonies on the
coasts of both the North and South Islands adjacent to seas rich in plankton, fish and marine
invertebrates. Red-billed gulls form pair bonds that can endure over many seasons, though
interbreeding with third parties is common. Occasionally they even interbreed with blackbilled gulls. These colonies can be densely populated and shared with other seabird species.
Competition for nesting sites is fierce with eggs frequently becoming casualties in territorial
squabbles. A nest is comprised of a mound of seaweed, grass, sticks and feathers with a
small depression at the top. Clutch size is usually 2-3 eggs. Incubation is shared by both
parents. Chicks fledge at 37 days old.
While most red-billed gulls live 6-14 years, they can potentially enjoy much longer lives. In
2009 a banded individual was found alive and well 28 years after it was banded.
Backyard Bird Monitoring Data
In April, backyard bird monitor Peter Field made the observation that song thrushes seemed
to be scarce, so I looked at our data and sure enough, he was right. Song thrush numbers
in April were down, as they were the previous two Aprils. Indeed, in April 2011, no one
recorded a single song thrush! After May’s surveys, I updated the graph and was delighted
to see their numbers up again, as one would expect from the previous two Mays. So, where
do song thrushes go in April? I’d love to hear your thoughts. One idea I had was that
perhaps they abandon our gardens in favour orchards at this time. Apparently, they are
partial to olives.
Average of 'most seen at one time'
Song Thrush averages from Garden Surveys 2010, 2011 & 2012 to date
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
2010
2011
2012