White washers of Whitewash Head

Press, 25 January 1979, Page 17

White washers of Whitewash Head

Potential danger lurks on Sumner Beaches during the second half of summer. Not Jaws 2, but two beaks. Young spotted shags drop to the water from Whitewash Head at this time of the year and being unable to fly, drift to the beaches. Although they look bedraggled and helpless, they should not be picked up by inexperienced people, because they vigorously defend themselves with sharp beaks and may attack a helper’s eye. Five other species also

nest in the cliffs according to G. Fenwick and W. Browne’s paper in the journal of the Royal Society of New Zealand. They are red-billed gulls, white fronted terns, starlings, rock pigeons, and black-back gulls. The spotted shag colony was well established at least 105 years ago when first recorded by Potts. About half the shag colony of about 450 birds breed each year. Mr B. Norris, of Sumner, a ranger, considers that 1968 was the year the number of birds peaked but the

decline that followed was halted three years ago. The number has increased since and he considers this may be the normal cyclical pattern of shag populations. The major nest building materials are ice plants and grasses from the cliff top, and dead branches. Seaweed is apparently not used. One of the pair builds the nest, the other collects materials, making as many as 10 trips in 40 minutes. Mating takes place during nest building. Egg laying extends over three

weeks from the middle of September and most nests have three eggs. Male and female spotted shags share incubation equally. The eggs are held on the feet and rolled every 15 to 30 minutes. The birds holding the egg have found the most efficient posture is to face into the cliff. This could be another reason for favouring the higher nesting ledges. Courtship displays stop after seven days incubation. incubation takes about a month and more than 90 per cent of eggs are fertile. Some, however, are lost over the cliff edge, especially during a changeover of incubating parent. When newly hatched, spotted shag nestlings are blind, weak, poorly co-or-■djnated, and naked, with a dark grey-black skin being the only covering until down appears at about five days. Chicks less than 20 days old die within 40 minutes if exposed to sunlight at a temperature greater than 32 degrees C. This temperature is commonly exceeded at Whitewash Head, so cooler, south-fac-ing ledges are chosen for nesting. Parents often stand on the sunward side of the nest; shading the chicks from direct sunlight. The spotted shag nestling begs for food by directing its bill at the parent shag’s head and by giving a high-pitched call at the same time. Nestlings feed on regurgitated food by inserting their beaks into the mouths of their parents. A feeding lasts 10 to 30 seconds, and as the nestling’s head disappears from sight it obviously

learns early to hold its breath when diving for food.

Soon after first light one parent from each nest flies out to sea from Whitewash Head; about

three hours later they return and feed the nestlings. Within 15 minutes the other parent goes. Most breeding birds make two trips in a day, with the chicks getting four feeds in the day.

Falling from the nest appears to be the main cause of nestling mortality and it appears to be slightly above 50 per cent at Whitewash Head. The wider ledges are not used because of accessibility to predators and man, hence the high loss from narrow ledges. The pattern changes about early January when chicks fledge at two months of age. High

breeding ledges, now well whitewashed, are abandoned for iedges near the

cliff base and the low promontory of the head receives its annual fresh coating.

Many Christchurch people will have seen the red billed gulls hovering in updrafts close to the cliff face. When a shag feeds its chicks these gulls approach, screaming loudly to upset the feeding

pattern and causing food to be spilt. The gulls swoop in to pick this up. Predators appear to be negligible on the cliffs. Black back gulls appear to leave them alone and cats are unable to reach many. The whitewashers of Whitewash Head appear to be coexisting with man successfully enough to ensure the name of the head need never be changed.

' By

RUSSELL KING