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Monitoring predators and chicks at Newport Wetlands Reserve PDF Print E-mail

NWR saline lagoon news , June 2014

The majority of the work this spring has been focused on breeding waders on the lagoons, specifically Avocet. The ratio of fledged chicks to adult pairs has been unsustainably low for all wader species for some time and Avocet have been a particular problem since 2008.

Previous breeding wader studies at Newport Wetlands have focused on nest monitoring of species nesting on the grassland rather than the islands. These studies have shown that hatch success is very high and that most of the chick mortality is occurring after the chicks hatch. Anecdotal evidence suggests that most chicks are lost in the first week or two. Despite hundreds of hours of observation less than 1% of chick predation has been witnessed and dead chicks found are even rarer.

With the help of RSPB research scientists we devised a method for monitoring predators, Avocet nests and Avocet chicks and then acquired the necessary licences from NRW and the BTO.

Mammalian predators were monitored by placing tubes with ink pads inside them on the islands so that any mammal that walked through the tube would leave prints. Other predators were observed by four trail cameras placed around the islands overlooking nests; these cameras had infrared lights and therefore operated by night as well as day. In addition to this we searched for Otter, Mink, Rat, Stoat, Weasel and Fox faeces when checking water levels or salinities. We also did timed watches of between 2 to 3 hours a day on average.

Nests were monitored by placing data loggers in the nests. The data loggers, which are about the size of three one-pence coins stuck together, record the temperature of the nest every ten minutes – in this way we can tell if the Avocet stopped incubating prematurely. When the eggs were due to hatch we physically inspected the nest to see how many eggs were hatching. Not all the eggs have hatched yet but nest success is over 90% and no predators were identified via the mammal tubes or the cameras; however, Rat prints were discovered on the lagoon 'coast'.

To monitor chicks we were heavily reliant on Dr Jennifer Smart from the RSPB, Richard Clarke, Vaughan Thomas, Jerry Lewis and Darryl Spittle from Goldcliff Ringers, Richard Facey from NRW and Roy Bamford. I’m grateful to all of them.

Chicks were caught when at least 10 days old as we discovered that their knee joints were not sufficiently large to take a ring before that age. One or two chicks in a brood were rung above the knee with a coloured tag over a BTO ring. A radio-tag about the size of a pea was then glued to the chick's back (see photo, courtesy of Richard Clarke). Of the ten radio-tagged chicks two were found under plucking posts thought to be used by a Buzzard, one was found in a Buzzard pellet, (see photo below, Richard Clarke), one chick fledged and the other six are still wearing theirs. The remaining radio-tagged birds are due to fledge and shed their tags by the third week of June. *

Next year I hope to radio-tag chicks in the first days of life, to discover what the main causes of mortality are during the first ten days of life.

* Author's update, September 2014: seven chicks (the six mentioned here plus a seventh which was fitted with a radio-tag taken from a dead bird) all fledged around the second week of June.

 

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Avocet chick showing colour flag and radio-tag, later found beneath a plucking post

Buzzard pellet with radio-tag antennae sticking out of it

Buzzard pellet with radio-tag antennae sticking out of it