Tag Archives: endemic

Will Climate Change cause Red Grouse Populations to suffer?

A twenty year study by the Game and Wildlife Conservation Trust (GWCT) shows that red grouse are laying eggs 0.5 days earlier each year, potentially harming their survival chances. As an endemic species, red grouse only exist in the British Isles, where they are an important game bird, and are managed due to loss of their heathland habitat.

The main concern earlier hatching raises for red grouse populations is trophic mismatch. This is where changes in population cycles occur, causing prey and predator species to be ‘out of sync’, with prey populations being lower than previously when predator populations are higher. Predator starvation or reduced survival prospects may result, as less food is available when needed. If red grouse chicks’ prey doesn’t coincide with chick hatching, the young red grouse may be left hungry. The warm weather seems to be driving craneflies – a key chick food – to be emerging even earlier than the chicks. This means even though chicks are hatching earlier, they may not be early enough for their prey and may still miss out. Even worse, early cranefly hatching can mean less survive to lay eggs for the following year.

Red grouse, Lagopus lagopus scotica - Alistair Young

Red grouse, Lagopus lagopus scotica, have been laying eggs earlier due to climate change. Image: Alistair Young.

As is often the case when climate change is considered, the effects on survival are even further complicated. The warmer springs produce more vegetation for red grouse hens to feed on, allowing them to produce more eggs. GWCT have found that hens laying earlier tend to have larger clutches, which could save the birds from decline.

As of yet, no overall effect on red grouse populations has been found.

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The birds and the bees in Hawaii: New study explore the effects of non-natives on ecosystem functioning

The more recent concept of monitoring restoration through ecosystem functioning has received support from scientists, but little practical study. New research by Hanna et al. (2012) studies the effects of invasive wasp species on plant pollination and fruiting in Hawaii.

Metrosideros polymorpha is an endemic flowering tree, historically pollinated by honeycreeper birds and bees. Honeycreepeer populations became threatened by predation from invasive spoecies, habitat degradation, competition and disease, causing population declines and extinctions. Following the decline of honeycreepers, and invasion of wasp species, Vespula pensylvanica, and introduction of the western honey bee, Apis mellifera, the non-native species began feeding on the nectar stores of M. polymorpha. V. pensylvanica is a non-pollinating insect; it reduces nectar availability to other wasps by defending a flower, where it stays, drinking the nectar and chasing away or hunting and eating pollinating bees. This reduces the plants fruiting success, as the wasp reduces the nectar supplies M. polymorpha produces to attract pollinators, and directly repels other insects, preventing pollination. A. mellifera, however, is known to pollinate some plants, though only those whose flower shape enables pollination transfer from the small honey bee.

Hanna et al. experimentally removed V. pensylvanica from selected sites, and recorded the effects on pollinaters and fruiting success. Visitation by pollinating insects increased, likely as predation risk decreased and nectar more available, which led to increased fruiting success. Both A. mellifera and endemic Hylaeus began visiting the flowers more often, but Hanna et al. believe they had differing effects on fruiting success. As A. mellifera visited more frequently, it would appear that they are more responsible for the increased fruiting success than Hylaeus, whose visitation rates increased less. A. mellifera could be acting as replacement pollinators following the drop in honeycreeper numbers, helping to sustain plant fruiting. Though this effect is postive for M. polymorpha, an increase in A. mellifera could increase competition with other pollinators, and may not be an effective pollinator of all plant species from which it takes nectar, especially ones which attract a less diverse range of pollinators.

This study emphasises the need to assess how species alter ecosystem functioning when forming management plans, and highlights the variability of impacts of invasive species. Hanna et al. suggest the next steps taken should be to assess wider effects of A. mellifera, and how V. penslyvanica affects pollination at different times of the season.

Hanna, C., Foote, D., Kremen, C. (2012), Invasive species management restores a plant–pollinator mutualism in Hawaii. Journal of Applied Ecology.

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