Monday, 28 August 2023 05:56

Lesser noddys check into Cousin Island for the breeding season

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Breeding success monitoring helps to keep track of the populations Breeding success monitoring helps to keep track of the populations

It’s early morning on Cousin Island Special Reserve. You sit on the veranda of the field station, sipping coffee and scaring off Seychelles fodys and skinks determined to grab a piece of your breakfast. As you stare off into the sea, you notice a flock of Lesser Noddys (Anous tenuirostris) close to shore.

Moving closer, you realize that the dense flock is also having its breakfast, so to speak, dipping and picking off fish from shoals pushed onto the shore by currents. A banquet has been served right on the beach.

The birds nest communally in huge colonies and their presence on the island signals the breeding season. From May to September of each year, which coincides with the Southeast monsoon season, thousands of these birds check into Cousin Island.

They occupy every available tree across the island, especially the plateau forest, and overwhelm the senses with bird sounds and bird poop.

Pairs can be seen flying together in courtship and zigzagging close to each other.

They build their nests with native Pisonia grandis (Mapou) leaves and seaweed. You will see birds on the ground searching for suitable leaves for nest building. They will pick up and discard some, before flying into the trees with the most desirable ones. Females are notoriously picky about materials and reject unsuitable leaves or twigs.

The female lays a single egg. Incubation lasts approximately 35 days and chicks fledge at 55-70 days.

During this time the island staff carry out their census and breeding success monitoring.

Monitoring is done once every week using a standardized seabird monitoring protocol. It begins when nest building is near completion and egg laying is underway, and ends when nests have fledged chicks.

Using a swivel mirror on a pole, staff check the contents of sample nests, taking care not to flush an adult off the egg or cause a chick to fall out of the nest.
They record the presence of one or two adults, and the various stages of the chick: a small downy chick, a partially feathered chick, or a near or fully feathered chick.

Keeping track of lesser noddy breeding success over time is an important part of monitoring the species. The species, along with other seabirds, is an indicator species that helps assess the ocean's health.

Their populations respond to fluctuations in fish stocks, pollution events, climate change, and shifts in ocean currents or feeding grounds.
For example, the decline in fish stocks as a result of overfishing has been observed to affect seabird populations as the birds travel further to find food, which is necessary to successfully raise chicks.

Over the past few years, climate change and ocean current shifts have become more prevalent, resulting in historical feeding grounds being moved or disappearing, and breeding seasons being shifted.

Pollution events may lead to colony failures, especially when feeding grounds are affected.

The monitoring on Cousin has shown that in periods of unfavourable weather conditions, there are more egg losses.

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