Climate change disrupts natural relationships between species

Golden plover. Photo by Mick DrydenFrom BTO

Climate change is having dramatic effects on many of our species, and not always in obvious ways. A new study demonstrates that climate change disrupts natural relationships between species. Part II of The Intergovernmental Panel on Climate Change (IPCC) fifth assessment report, published at the end of March, reported that climate change is altering species’ distributions and populations with high confidence. However, what is less clear is how and why. Latest research led by the British Trust for Ornithology (BTO) shows that the main driver of change might actually occur through altered interactions between species, rather than direct responses to climate.

Each species shares an ecosystem with other species, some of which it might eat, and others that might eat it or compete with it. Scientists from the BTO and other partners of the Cambridge Conservation Initiative (CCI) found it was the effects of climatic changes upon the populations or activity of these other species which were responsible for many of the impacts observed, as they cascade through the food chain. For example, Arctic fox populations have been affected by declining lemming populations linked to changes in snow cover, and also by expanding red fox populations. Hungry Arctic foxes may look to other prey such as breeding wildfowl like brent goose and waders like sanderling  (they already feed on these birds during ‘lemming years’ – in Jersey we don’t see any young geese at all some years). In the UK, upland birds such as the golden plover are affected by increasing summer temperatures, which causes problems for their cranefly prey. These disruptions particularly affect predatory species, and appear to have worsened with climate change.

Dr James Pearce-Higgins of the BTO said, “Although it might be assumed that most species are responding directly to climatic changes, either as individuals move to keep within their favoured climate zone, or through survival and reproductive rates linked closely to these climatic variables, this does not account for the majority of impacts. Instead, the main impacts of climate change occur through altered interactions between species within an ecosystem.”

Importantly, as much conservation action is already about managing species’ populations, such as controlling invasive species or reducing predation risk, we already have the conservation tools in place to reduce the impacts of climate change on species. This understanding, therefore, provides hope that we can help the most vulnerable species adapt to climate change, providing the magnitude of climate change is not too great, and that conservation activity is sufficiently funded. For example, in the UK uplands, we can restore degraded peatland habitats to boost invertebrate cranefly populations, and increase their resilience to climate change. Whilst this work also helps identify the types of species’ most vulnerable to future climate change impacts, there remains a lack of information from the tropics, where most species’ occur, and where increased monitoring and research is essential.

“This study highlights a need to consider the often complex ecological relationships between species when assessing the impacts of climate change on wildlife.” says Jamie Carr of the International Union for Conservation of Nature, a co-author on the study. “Most research to date has focused on the direct impacts of changing conditions, which may mean that important emerging threats are being overlooked.”

The report can be seen here Brent goose. Photo by Mick Dryden

Calling all puffins

Ramsey Island's decoys and sound system. Photo by Greg MorganFrom Ramsey Island and Grassholm

This month saw the start of an innovative project in local waters aimed at trying to lure puffins back to Ramsey one of the Pembrokeshire islands and an RSPB reserve. Puffins used to breed on Ramsey in the 1800’s but with the arrival of rats through shipwrecks their days as a breeding species on the island were numbered. Rats are, as we have seen on other islands (see here and here for other local examples), voracious predators and when they find their way onto seabird islands their impact is devastating. Millions of years of evolution have seen some species of seabird adapt to breed in burrows underground. This allows them to avoid avian predators such as gulls but when you suddenly introduce an alien mammalian predator to which they have no defence the impact is catastrophic.

Work 14 years ago by RSPB and Wildlife Management International meant that the introduced rats were finally eradicated. The response of Manx shearwaters has been impressive with an increase from 850 pairs in 1999 to 3,835 pairs in 2012. Storm petrels were recorded breeding for the first time in 2008 but puffins have not made it back yet

Greg Morgan and the sound device. Photo by Michael HoffmanFour years ago, decoy puffins were put out on Ramsey’s cliff tops in the hope that they might attract puffins regularly seen at sea around the Island (there is colony nearby at Skomer Island) but with no success. However, seeing the responses of puffins at Copeland Island where sound was added a couple of years ago it was decided to try this approach on Ramsey. Nigel Butcher, ace technician in the Conservation Science Department at the RSPB made the sound system which plays the call of a puffin on a repeat loop from a loudspeaker (very loudly!). German technology then completed the outfit when Michael Hoffman, one of Ramsey Island’s regular and very talented volunteers made a sturdy frame on which to securely site the device plus a solar panel to keep the battery topped up.

The decoys accompanying the sound system were made by Ed Tycer. It is hoped these will act as an added attraction if birds make landfall.

The system was trialled last year for a short, four-week period, with some success whilst dealing with early teething problems. Birds were recorded making landfall on low tide rocks below the speaker and on one memorable occasion eight birds landed on the cliff tops among the decoys. With the device out for a full season this year it is hoped the project can build on this success and see puffins return to their rightful place on the Ramsey Island breeding bird list.

Could a project like this work in the Channel Islands? Well, yes, in theory it would be well worth trying. However, where is there suitable puffin-friendly ground that has no rats? That is pretty scarce and the best current puffin site, Burhou, probably already has space for more puffins anyway. But, with tiny colonies away from Burhou only barely surviving, could birds be lured to safer spots? That might well be worth trying – but first, get rid of those pesky rats!

Birds On The Edge is grateful to Greg Morgan for help in producing this report. You can follow the Ramsey puffin story at the Island’s blog and even on Twitter @RSPBRamseyPuffin decoys on Ramsey Island 2014. Photo by Greg Morgan

Keep a look out for wandering choughs

Red-billed choughs. Photo by Mick DrydenChoughs are well known for not moving around much. Well, so it’s generally thought. Actually, on the quiet, they get round quite a lot.

A lone unringed chough was photographed on 16th February, feeding in the fields behind the cliffs east of the Otter Estuary, Budleigh Salterton, Devon. Possibly the same bird was seen not too far away on 23rd March at Exmouth, Devon.

Another chough was reported in the Scilly Isles again where a single, unringed, bird was spotted on Bryher near Popplestone Bay on 4th April. The bird was later seen on Tresco and had reached St Martin’s by the evening. The last chough in the islands was seen on St Martin’s and later at Peninnis on St Mary’s (report here). Of the six sightings in Scilly, three have been in the last decade, with one in the 1980s.

However, perhaps the most exciting report comes courtesy of our great friends at Cornish Choughs

When choughs returned naturally to Cornwall in 2001 it was thought that the intrepid colonists had come across from Brittany. It turned out, remarkably, that they were from southern Ireland (we know this thanks to DNA work by Aberdeen University – abstract here). However, and very excitingly, Cornish Choughs can now confidently report there is at  least one Breton chough in Kernow (Cornwall) adding to the Celtic melting pot of choughiness (technical term).

Towards the end of February Cornish Choughs were contacted by Rob, one of their small team of ‘just-in-case’ chough watchers in North Devon to say he had found a chough at Baggy Point. Rob got some lovely images and they showed the chough was colour-ringed but the rings were not ones they recognised. After checking with colleagues working with choughs in Wales who said ‘no, not one of theirs’, a quick email was sent to friends across the water in Brittany to see if they could identify the bird.  Sure enough, yes they could!

It turns out this chough was ringed as a nestling on the island of Ouessant in 2007.  It was known to have been resident on the island until at least 2011, and could well have been there in subsequent years too, as monitoring in Brittany is not as intensive as it is in Cornwall.

The chough then disappeared from Baggy Point after a couple of days (where it was happily feeding alongside some Hebridean sheep), but was ‘refound’ by Rob again in the same area towards the middle of March.  It all too soon vanished, but not for long though. Recently another keen chough watcher saw a chough in north Cornwall and sent her record in to CBWPS, who of course forwarded it on. As no chough was expected to be in that place, local chough watcher Geoff was asked to go take a peek and within minutes it was confirmed to be the same Breton bird. How amazing is that!

Well, that does mean that at least one of those birds in the UK sneaked right round the Channel Islands! Or fly through them? Of course it also highlights just how important observers are and how valuable their records are to all our chough projects. It is easy at times for people to think that we know where all ‘our’ birds are. However, even those with radio transmitters can get around when the team aren’t looking and all reports can help us. So, never feel your records won’t be of interest, look at our page about chough identification and contact us through this address birdsote@gmail.com.Cornish chough. Photo by Bob Sharples www.bobsharplesphotography.co.uk

Guernsey launches new code of conduct to protect seabirds and marine mammals

Common tern. Photo by Romano da CostaThe Environment Department, La Société Guernesiaise and Guernsey’s RSPB group have launched ‘Give Wildlife A Chance’ a code of conduct created to raise awareness of the internationally important seabirds and marine mammals that live and breed in and around Guernsey. The Code encourages people to observe guidelines to prevent the unnecessary disturbance of birds and seals around their breeding and feeding sites.

Kayakers and boat owners are being asked to take special care to keep their distance from the seal breeding and haul out areas around the Humps and Les Hanois.

Temporary signage will be placed around the most sensitive seabird breeding sites in Guernsey including Jerbourg, the south coast cliffs and Pleinmont. The signs will be in place for the duration of the breeding season which runs from 1st February to 31st July. The most vulnerable species of seabirds breeding in Guernsey and the surrounding Islands include terns, puffins, guillemots, razorbills, shags, cormorants and oystercatchers. It is also very important not to disturb gulls from their traditional breeding sites on the south coast cliffs and islets as they then may move into St Peter Port and other urban areas and start to nest on roofs, which would bring increasing conflict with people, something we would all wish to avoid!

Many of these species have been seriously affected by the high winds and heavy seas during the extended period of storms earlier in the year. A mass seabird wreck (high mortality of seabirds) was experienced in the subsequent weeks, with over 30,000 dead seabirds being recorded washed up in UK, France and Channel Islands (see our report here). The worst affected were auks (puffins, guillemots and razorbills) with over 15,000 puffins recorded as dead.  Whilst there were few post mortems a large number were recorded as in very poor condition and considered to have died from a combination of exhaustion and starvation as they were unable to feed.

Previously the most comparable mass seabird mortalities in our region were the Torrey Canyon oil spill disaster in 1967 and Amoco Cadiz disaster in with 15,000-20,000 reported dead during each incident – possibly half the number recently recorded as washed up on beaches following the severe storms.

It is hoped that with the introduction of the ‘Give Wildlife A Chance’ code of conduct as many people as possible will be aware of the special significance of the Guernsey sites, and in particularly the need for breeding seabirds and seals to be left undisturbed. It’s likely that this will be a very difficult breeding season for many seabirds as many birds remain in relatively poor condition. However, if they are able to recover with as little disturbance from human activities as possible it may be possible to regain the numbers of birds lost although ornithologists acknowledge that this may take many years.

Donna Francis, the Guernsey RSPB group leader, said, “Birds that are disturbed while trying to breed waste valuable energy at a time when they are trying to raise their young. Some species may abandon nests and chicks if sites are regularly subject to disturbance. Hopefully ‘Give Wildlife A Chance’ will increase people’s interest and help make them aware of the birds’ needs and how they can protect them.”

Environment Minister, Roger Domaille said “The Environment Board fully supports the introduction of ‘Give Wildlife A Chance’ – our seabirds are the most iconic wildlife Guernsey has and many people are unaware that the Bailiwick is a breeding outpost for some very vulnerable species such as puffins which are reduced to a handful of breeding pairs now. I’m delighted to see the launch of this code of conduct to help reduce disturbance to wildlife and as such it addresses one of the action plans identified in the proposed Biodiversity Strategy for Guernsey”.

This is the first of a range of initiatives to be implemented in order to help enhance and conserve Guernsey’s wildlife and natural landscape.

Download Give wildlife a chance here

In Jersey you can download:

Jersey Marine & Coastal Wildlife Watching Code here

Plémont to Grève de Lecq seabird protection zone leaflet here

Écréhous seabird protection zone leaflet here

Atlantic grey seal. Photo by Regis Perdriat

Jersey’s choughs out and about again

Red-billed chough. Sorel 9-4-2014. Photo by Mick Dryden On Wednesday, 9th April, we began this year’s programme of acclimatising the choughs at Sorel to the world outside of their aviary. All eight birds were given access and, unlike like last year, all eight birds were outside within about 30 seconds. They then went on to give us a spectacular show of flying and calling – five birds went together about as high as they could, becoming black spots against the clouds, calling all the time. Since Wednesday the birds have returned, mostly, to a familiar pattern involving the quarry at Ronez and flights back to the aviary.

However, there is some wandering going on and, even though each bird has a radio transmitter, we don’t always know where they are or where they have been throughout the day. So, please, if you see a chough anywhere, feel free to let us know when and where you saw it – your record could help fill in a gap in our understanding or what they do and where they go throughout the day. Let Liz or Glyn know about your sighting and also visit the Seen a chough? page here which gives helpful hints on ID etc.Red-billed chough. Sorel Point 10-4-2014. Photo by Mick Dryden

Chough report: March 2014

Sunset, Sorel, and sleepy choughs. Photo by Liz CorryBy Liz Corry

March was a busy month with the arrival of the breeding season and the necessary preparations for the next round of releases.

Breeding programme at DurrellSorel sheep provide nesting material for choughs. Photo by Liz Corry

With all three pairs settled into their breeding aviaries, nesting material was added. Keepers provide the choughs with all the materials they would naturally use in the wild. Twigs, heather, moss, sheep’s wool, and horse hair are all added in carefully timed stages so the female chough can build the perfect nest.

This year wool from the Manx Loaghtan sheep at Sorel has been added to the mix. Just one of the bonuses of having the sheep temporarily housed in the aviary field. Strands of wool were collected from the fence posts and mesh where the sheep itch away their woes. The wool is disinfected once back at Durrell and checked for ticks before adding to the aviary.

It is evident from the nest cameras that the inexperienced female has the blueprints in her head to design a nest, but lacks the finesse of the seasoned professionals. Although, saying that, no nest ever appears to be perfect as the females are continuously making amendments. They have yet to start egg laying, but keepers expect to see the first egg any day now.

Nesting choughs. Photos by Liz Corry and Catherine Francescon

Choughs at Durrell are busy constructing their nests. Gwinny lays the foundations of her nest (top left). Issy collects wool and horse hair to line her almost complete nest (top right). Experienced breeder Gwinny (bottom left) has an almost perfect nest, whilst the young female Black scores an ‘A for effort’ (bottom right).

Spring at Sorel

Spring is in the air at Sorel. Photo by Liz CorryThe weather finally gave us all a bit of a breather this month and allowed essential maintenance work to be carried out on the aviary. Trevor Smith and Gavin Raffray from Durrell’s Maintenance team helped with the list of jobs.

The priority was getting the roof covered over the shed sections to provide the birds with extra shelter and stop the food-bowls from being drowned. There were a few fence posts to re-align thanks to the sheep. Hinges were oiled and rusted hatch wires were replaced with plastic coated steel wire.

I am contractually obliged not to talk about what happened when the guys finished working….but there is no clause about use of photographic material.Jersey’s roadside assistance insurance plan paid off. Photo by Liz Corry

A vain attempt to be more environmentally friendly saw a water collection butt added to the aviary. Water usage at the aviary averages 10 litres a day. Current design of the aviary means that only a small section of guttering was added. Whilst this might not be effective it should provide water for cleaning purposes and reduce the quota of fresh water carried up to the aviary. The equipment was donated by members of the public.

The ‘lawn’ needed addressing as the choughs were beginning to get lost in the undergrowth. In the wild, the grassland needs to be kept short (<5cm) to benefit the choughs. It allows the insect communities to thrive and thus become a sustainable food source for insectivorous birds like the chough. Whilst the captive choughs will never go short of food, they need to be able to practice natural skills such as soil probing.

The manual lawn mower couldn’t quite hack it, so the lawn was attacked with a petrol strimmer. Surprisingly no comments were made by the public on a sunny Sunday afternoon when a young lady strode with purpose, and a petrol can, along the cliff path of Sorel. Personal investment in a battery powered strimmer has relieved the public of any future unexpected sightings.

Vet visits and pre-release health screening

Radio transmitters and ID rings were added to those birds that needed them. Photo by Liz CorryRadio transmitters arrived for the four birds who needed them (Mauve, who lost hers last September, and the three new birds). So, at the start of the month there was a catch up to attach the transmitters. The new birds also had Jersey branded leg rings and colour rings attached.

Whilst in the hand, it provided Durrell’s vet team the opportunity to obtain blood samples to screen any potential health issues. All eight birds had blood samples taken and a three day, pooled, faecal sample was also taken for the group.

A hood (old sock) is placed on the bird’s head to calm them down whilst in the hand. Photo by Liz CorryThe screening showed the continued presence of Syngamus (gapeworm) so the birds were given a course of Ivermectin. This involves yet more catching since injection is the only guaranteed way of administering the drug to each bird in equal dose. The bird is given one injection in the pectoral muscle and a second 10-14 days later. Further faecal samples were taken to monitor the effect of the drug on the parasitic load.

Student placements

At the start of the year an advert went out for student placements on the chough project. Durrell regularly take on University students looking to gain accreditation towards their degree. The chough reintroduction project is looking for students to radio-track released birds, assist with research projects, and potentially assist with the captive birds.

The first to take up such a position was Adam Dallas-Chapman from Jersey. A recent graduate of the University of Bath, he will be with the project for three months and has already got stuck into radio-tracking practice.

Pierre Rauscher, from France, will be joining Adam in mid-April. He will also be spending three months in Jersey using his time on the project to contribute to his degree certification.

There are still positions available between June and September. For more information and to apply visit Durrell here.

Newest team member

Durrell has been awarded funding to employ a field assistant on a twelve month contract. They will be assistting with the release and radio-tracking of the choughs whilst continuing to help with the captive breeding programme.Harriet Clark, Chough field assistant 2014

Harriet Clark, currently a bird keeper at Durrell, will be joining the Conservation Department in April. Harriet has experience working on the Mauritian reintroduction projects and is currently training to be a licensed bird-ringer. No doubt she will be a valuable asset to the project and both staff and birds will benefit from her enthusiasm and dedication.

April volunteer activity

St Peter's Valley. Photo by National Trust for Jersey

Sunday 13th April 2014 – St Peters Valley  – 10.30-13.00

Hemlock water dropwort management

From Jersey Conservation Volunteers

Dear volunteers,

The penultimate task of the season is already upon us, how time flies!

The details

Hemlock water dropwort Oenanthe crocata  is trying to take over the wet meadow in St Peter’s Valley, next to the mill pond. So, the task will be to cut and remove as much of this as we can, before it swamps the grasses and wildflowers.

Hemlock water dropwort is a wet meadow specialist, with delicate, white, frothy flowers, that are a favourite with hoverflies and other insects, and can grow to 4 or 5 feet high. Whilst it is a pretty plant, the roots are highly poisonous, so we need to try and remove them from this meadow before it can be grazed this summer.

The site

The meeting point will be in the mill pond car park, just past the Victoria Pub, on La Vallée de Saint-Pierre (St Peter’s Valley), please arrive by 10.15am, for a 10.30am prompt start. There are some parking spaces in this car park; however, more parking is available at La Moulin de Quetival, or in the pub car park.

The task

Our job will be to cut the hemlock foliage down, to weaken it, rather than pulling it up by the roots, so please bring any sickles you may have, or other cutting implements.

Tools needed

We will be able to provide some tools and gloves, but please bring your own if you have them to make sure we have enough to go around.

Clothing needed

Please, please, please wear long sleeves, whatever the weather, and gloves; it will be wet underfoot, so wellies are a must.

And of course, no Jersey Conservation Volunteer task would be complete without the provision of tea & cake, courtesy of Kim.

Chronicle of a Jersey seabird wreck

Puffin. Photo by Harriet WhitfordBy Cris Sellarés

In late March 2014, Jersey hit the mark of a thousand dead seabirds found on its shores; the Island total since reaching 1,022 with numbers in the Channel Islands overall to just under 1,300 birds.

In a regular winter we might expect between 10 and 40 dead seabirds on our shores over a few months, recorded by a few local birdwatchers that check the beaches regularly. But this year was different, and even when we did start to realise that things weren’t quite as usual, we never suspected we’d end up with over one thousand dead birds in Jersey alone. This kind of event with so many dead seabirds is known as a wreck.

Razorbills. Photo by Harriet WhitfordIt was late January when numbers began building up and we started finding dead birds by the dozens in single stretches of our coast. Other birds were found still alive and taken to the JSPCA. At the same time, members of the public started to report dead birds, asking why this was happening and wanting to help and become involved. A record system was set up with Dr Glyn Young from Durrell taking in the records via email, the Jerseybirds website or the Jersey Wildlife Facebook group. A protocol for photographing the carcasses and disposing of them was advised to the general public, so that the identification of the species could be confirmed and so that the same bird wasn’t reported again by another person.

As awareness of the wreck spread, more people started to look for birds to report. Predicting a surge of reports over the weekends, we set up a series of co-ordinated surveys on four consecutive Sundays. These searches involved a team of 25-30 volunteers checking sections of the Jersey coastline, collecting all the birds found and taking them to an arranged collection point, where carcasses were laid out, identified and examined. Much information was gained from these counts, as well as allowing many people see some bird species for the first time: such as razorbills, great northern divers, grebes, kittiwakes, and, of course, puffins, which were instantly recognizable with their tuxedo suits, short yellow feet and colourful beaks. Indeed it was a very sad occasion that many people commented on, that the first puffin they or their children had seen was a dead one on the beach.

Ouaisne dead bird count 16th February 2014. Photo by Tim RansomWith the numbers from surveys and individual reports piling up, a worrying picture started to develop, encompassing rare finds (common scoter, red-necked grebe, little auk) and ringed birds whose origin could be traced to colonies in Skomer Island, the Hebrides, Orkney, France and, for many shags, the Channel Islands.

Some birds that were examined post mortem were found to have drowned, starved, or both; while samples, frozen carcasses and photographic evidence were sent to various UK-based scientists to contribute towards their long-term research.

Many questions have arisen from this environmental disaster, here are some answers gathered from the scientific community.

Jersey seabird wreck 2014. Table of casualtiesWhat species have been affected?

Auks (guillemots, razorbills and puffins) made up the largest portion of the casualties, with significant numbers of shags, great northern divers, kittiwakes and gulls following behind. Here is a breakdown of the birds found in Jersey.

The combined total of all reported birds from the coasts of UK, France and Spain is a horrifying 32,156, which is a conservative minimum as many birds may have sunk in the oceans or been grounded on inaccessible shores. On top of that, news from France suggests this might still go up by 5,000 at least.

Seabird casualties in Jersey 2014What is the cause of these deaths?

The unusual series of strong storms we saw this winter are to blame. Most seabirds spend these months at sea, moulting their flight feathers and feeding. The storms would have weakened them and make diving for fish difficult in high waves and 100mph winds. The effects of the storms did not cease after the bad weather, as the waters remained murky for many weeks, making fishing still difficult. Unfortunately, these storms have been predicted to increase in strength and frequency as part of new meteorological model accounting for climate change.

Seabird deaths. January to April 2014Thankfully, the number of reported birds has started to decrease as you can see on the graph. The columns in green mark survey dates, the ones in pink mark reports in bulk.

What effect will this have on seabird populations?

The effect this wreck has had on the populations of seabirds will only be seen when the survivors return to their breeding colonies in the UK, Scandinavia and other parts. Only then local researchers will be able to quantify the effect the storms have had on the breeding populations.

What are we doing about it?

Adult shag. One of Jersey's breeders? Photo by Amanda ShawActions have been taken across the Channel Islands since news of the seabird wreck started to spread. In February a conference call was held between organizations and governments of the different Islands to discuss the findings and possible impacts on our breeding colonies. A few weeks later a workshop was organized by the Alderney Wildlife Trust that got together bird experts and vets from Guernsey, Jersey and France, to discuss survey methods and carcass examination techniques.

Great northern diver. Photo by Amanda ShawThe Alderney Wildlife Trust has also set up a webpage (here) to report birds found on the beaches and thanks to them the links between the islands and France have become stronger. We have established common protocols to monitor beaches that will allow us to detect future events such as a seabird wreck or a pollution incident, as well as standardizing carcass examination and data collection.

Beyond dealing with the wreck itself, a call has been made to local governments to support an islands-wide survey of our local breeding colonies as well as to step up the current guidelines of protection of our colonies against human-caused disturbance, which is one of the main factors affecting their breeding success.

PS. This report had 1022 words, one for each dead bird found in Jersey.

Collisions with low-rise buildings kill millions of birds each year

A bird left this trace after colliding with a window. Photo by Alan Hensel, Wikimedia CommonsFrom BirdWatching

For years, it has been assumed in the United States that a staggering number of birds die in collisions with buildings – between 100 million and one billion every year.

The total is often cited as fact, even though it was presented, in 1990, as only a rough estimate.

Now, thanks to a systematic review of published studies and unpublished collision-monitoring datasets, not only is that estimate true, but also that low-rise buildings and residences kill more birds than skyscrapers. What’s more, mortality caused by building collisions may be having an effect on populations of vulnerable species.

Between 365 and 988 million birds are killed annually by building collisions in the U.S., say researchers of the Smithsonian Migratory Bird Center and U.S. Fish and Wildlife Service’s Division of Migratory Birds.

“Results support the conclusion that building collision mortality is one of the top sources of direct anthropogenic mortality of birds in the U.S.,” they conclude. “Among other national estimates that are data-driven and systematically derived, only predation by free-ranging domestic cats is estimated to cause a greater amount of mortality.”

Collisions with buildings 4-11 stories tall account for roughly 56 % of overall mortality (339 million deaths, on average), say the analysts. Residences – detached houses and multi-unit residences 1-3 stories tall – account for 44 % (253 million), while high-rises, buildings at least 12 stories tall, cause less than 1 % (508,000).

Residences kill birds at a lower rate than high-rises – 2.1 vs. 24.3 birds per skyscraper – but residences vastly outnumber high-rises. The findings suggest that reducing mortality substantially will require mitigation measures to be applied across a huge number of structures.

This is not a problem restricted to North America, buildings and other man-made structures kill birds across the world and may reduce further populations of already threatened species. The report can be downloaded free of charge here