With the terrestrial surveying season now in full swing, our ecologists have dusted down our equipment and headed out across the country on a myriad of different surveying projects using a range of innovative ecology survey techniques.

One of our key pieces of kit for carrying out a bat survey is our GoPro, which is a waterproof, HD-quality video recorder. Small and compact, we can attach this device to a helmet or pole to film footage from the top of trees, inside of lofts and many other locations.

This video shows our Technical Director Carlos Abrahams assessing a tree for its potential to support bat roosts and searching for evidence of roosting bats. It demonstrates the climbing ability and strength our ecologists need for this type of survey!

Tree climbing surveys are conducted by our CS38 qualified tree-climber and licensed bat-worker ecologists. Firstly, a daytime visit will be made to the site to identify trees within the work areas which appear to have roost potential and will require a tree climbing bat survey. Following this ground-based assessment, a tree climbing bat survey, as Carlos carries out in the video, will be carried out for all trees with moderate or high roost potential.

As part of this bat survey, any suitable cavities should be fully inspected using an endoscope. Where this is not possible, then an additional bat survey (such as an emergence survey) might be needed. A survey report will be produced to detail the ground-based, treeclimb and emergence (where required) study methodologies and results, providing an initial assessment of potential impacts and making recommendations for any necessary further survey work and/or mitigation measures.

Our Technical Director Carlos Abrahams conducting tree climbing bat survey

Our Technical Director Carlos Abrahams conducting tree climbing bat survey

For any bird, successfully raising chicks can be a tricky business, particularly for a ground-nesting bird such as the curlew (Numenius arquata), Europe’s largest wading bird. The curlew is listed as ‘near threatened’ by the IUCN and is a UK BAP (Biodiversity Action Plan) priority bird species due to the international importance of breeding and wintering UK populations, so when our Ecologist Martin Ledger found a curlew nest with eggs during a breeding birds survey, he documented what he saw. Following his second visit to the nest, he is still debating whether the eggs he originally found had successfully fledged or been predated, most likely by a hedgehog.

The evidence

On Martin’s first visit, he found a curlew nest hidden in the grass.

Location of curlew eggs

Location of curlew eggs

Inside the nest were four unhatched eggs. Curlews typically lay between three and six eggs, which are incubated for around a month before hatching.

Four unhatched curlew eggs

Four unhatched curlew eggs

Six days later, when Martin returned, he found the scene shown below: the eggs had either hatched or been predated. If predation was the reason for the broken egg shells, Martin believes that hedgehogs would be the prime suspect, as broken egg shells are a common trait when hedgehogs predate a nest, whilst other predators generally leave less mess.

Curlew egg shell remains

Curlew egg shell remains

However, finding egg shells and no chicks in the nest doesn’t necessarily mean the nest was predated. Curlews are usually precocial, meaning that the chicks generally leave the nest as soon as they are born and find food for themselves in thick cover, whilst they wait to develop their flying feathers. So the chicks could have hatched successfully and made a quick getaway!

The jury is still out on whether these curlew eggs hatched and fledged, but either way it has made for a lively debate and given us a further glimpse into the breeding life of a curlew.