Robben Island
|
Robben Island Bird Highlights of 2001
|
We list some of the interesting bird observations which occurred during
our fieldwork on Robben Island in
2001. An overall account of the birds of Robben Island, and a
birdlist for the island, can be found in Wildlife of Robben
Island, by Rob Crawford and Bruce Dyer, and published by the
ADU as Bright Continent Guide 1.
Ostriches at Robben Island
|
- Ostrich: Two nests were found near the airfield. One
hatched 11 chicks and the other 10. By late November, most
chicks had survived and were a quarter of adult size. Kathy's
contretemps with a male Ostrich is recounted in the December 2001 issue
of the ADU newsletter, Bird Numbers in
The dangers of academic ornithology.
- African Penguin: In spite of the
Treasure oil spill of
June 2000, the 2001 nest count of penguins on Robben Island
exceeded the count of 2000 by nearly 18%; 6723 nests were
counted in 2001 compared with 5705 in 2000. The increase was
unexpected, but is attributed to the biomass of Sardines and
Anchovy, the two main prey items, being exceptionally large in
2001. A far larger proportion of penguins were able to breed
than in years of poor food availability. If the oil spill had
not occurred, the increase would have been even more
spectacular.
Three tightly packed rafts of at least 100 penguins each were
feeding between the entrance to the Victoria Basin and the end
of the breakwater at 1630 on 28 November. On dozens of trips
back and forth to the island, we have seldom seen more than a
few tiny groups of penguins along the first few kilometres
outside the port of Cape Town.
- Hadeda Ibis: Described by Rob Crawford and Bruce Dyer
as an "uncommon visitor", two were seen on a round island survey
on 12 August. They seem to have been on the island continuously
since then, with a largest count of three.
Cattle Egret
|
- The Heronry: The heronry was established in mid-August,
and by early September there were hundreds of breeding birds.
This year it was located in an impenetrable stand of Acacia near
the southwestern corner of the island, and it was extremely
difficult to estimate numbers. First to breed were Sacred Ibises
(several hundreds of nests), joined by at least six pairs of
Blackcrowned Night Herons and about 20 pairs of Little Egrets;
breeding by Cattle Egrets and Crowned Cormorants started a few
weeks later, both with hundreds of nests. Most Sacred Ibis
chicks had left their nests by the start of December, and there
were hundreds hanging around the edge of the quarry, and
hundreds more at Van Riebeeck's Quarry. At least two
Blackcrowned Night Herons fledged (seen on 15 November). In
December, most Cattle Egret eggs had hatched, but many were
still incubating. Most of the food brought to the chicks comes
from the mainland; it is striking to see a stream of small
flocks of Cattle Egrets and Sacred Ibises arriving onto the
island from over the sea. Most birds make the shortest crossing,
7 km from Milnerton, which means flying straight into the teeth
of the southeaster. It is amazing that feeding on the mainland
and breeding on the island can be energetically cost effective.
Blackcrowned Night Heron
|
- Blackcrowned Night Heron: One left the island at
right angles to the coastline, taking the shortest crossing
towards the mainland, at 1900 on 4 December.
- Black Sparrowhawk: One swooped low over the airfield
on 2 November, causing mayhem among the dozen or so Crowned
Plovers which nest in this area.
- Chukar Partridge: Although this introduced species
seems to be coming more widespread on the island, breeding is
seldom recorded. There was a family party along West Perimeter
Road on 29 November 2001.
- Indian Peafowl: Male displays were first observed on
25 October. After this date, vocalisations were heard more
frequently, mostly from the woodland in the centre of the
island, near the prison. Two peahens were flushed from the
quarry in the penguin colony on 29 November; we have never seen
them in this area before. No chicks were seen.
- Waders:
Four wader counts were made along the perimeter of the island
between November 2000 and August 2001, two in summer and two in
winter. These have been summarized and published in the Wader
Study Group Bulletin (December 2001, no. 96, pp 37-39).
The largest totals ever of African Black Oystercatchers was
recorded on round island surveys on 29 November and 5
December, when 158 and 156 were counted, respectively. The
previous maxima had been 149, counted by Phil Whittington on 26
December 1998, and 143, counted during one of the four 2000/01
surveys on 3 March 2001.
Of the resident waders, breeding
was recorded for four species of plover (Blacksmith, Crowned,
Kittlitz's and Whitefronted), and for Spotted Dikkop and African
Black Oystercatcher,
- Kelp Gull: The first breeding record of Kelp Gull on
Robben Island was made in November last year, when one pair bred
in the quarry at the northeast corner of the island. This year,
the first nest to be found was on the shoreline about 100 m to
the west of the quarry; this nest had a hatchling and an egg on
15 November. By early December there were 14 nests in the
quarry. Kelp Gulls are serious predators of eggs and small
chicks on most other seabird species, so the advent of nesting
last year, and the increase in numbers this year, is not one
that seabird ornithologists are at all enthusiastic about.
- Hartlaub's Gull and Swift Tern:
Neither of these autumn-breeding species nested in 2001,
possibly because of the population of feral cats on the island.
The last year in which Hartlaub's Gulls bred, 1999, was the year
in which cat numbers were brought down to just a handful;
unfortunately the programme was not completed at the time, and
the size of the cat population is increasing.
- Sabine's Gull: There were thousands just offshore of
the northeast corner of the island for several weeks in March
and April. Although sightings around Robben Island in autumn are
common, this years flocks were larger than usual and stayed for
longer.
A couple of hundred birds were observed from the
ferry between 25 October and 3 November just beyond the
breakwater to Cape Town Harbour, but they left the area soon
after this. Sabine's Gulls are not often seen inshore in large
numbers in spring. These Sabine's Gulls are believed to breed in
the Canadian arctic, but there are no ring recoveries to prove
this.
- Namaqua Dove: Three near the shore in the settlement on 5 December.
Our research on Robben Island is supported by the Darwin
Initiative, Earthwatch Institute, National Research Foundation,
University of Cape Town and University of Groningen. Marine and
Coastal Management and the Robben Island Museum provide
logistical support.
This article was originally published in Promerops 250: 17-18.
Promerops is the newsletter
of the
Cape Bird Club.
|
