News archive

October 2015

Wednesday, 21 October 2015

Female great tit

Research: Divorce in birds is affected by their social group

Whether a pair of birds will 'divorce' or stay together after they first breed is influenced by the social environment in which the relationship is formed, according to a new study by researchers from Oxford University.

Much like humans, birds tend to be socially monogamous: they find a partner to mate with and remain socially exclusive with this partner. But, also like humans, they sometimes cheat on their partners, or separate to mate with someone else  and this often happens when the social partnership is sub-optimal.

The mating choices of birds are naturally affected by their social environment, because it determines the number and availability of potential partners they can choose from. "Humans find it easier to find a suitable partner if they've got lots of friends and live in a big city," said Dr Antica Culina, from the Department of Zoology, who led the research. "It's similar for birds."

Most studies that attempt to understand the social dynamics of separation in birds have been based on population-level data, due to the difficulty in obtaining enough information about the interactions between individual birds in the wild.

However, a team from Oxford University has studied thousands of individual Great Tits at Wytham Woods, Oxon, since the 1960s. Since 2007, these birds have been included in a large-scale study to understand their social behaviour, with 80 per cent of the tits that spend the winter in the woods tagged with passive integrated transponders (PITs).

The team has a series of feeders around the woods that are equipped with PIT-detecting antennae. When a bird lands on one, its presence is recorded along with the date and time. As flocks of birds come and go, the team can identify which birds regularly socialise with each other, and infer the strength of associations between pairs of birds.

"Our feeders are opened once a week for two days, and in this way we can capture a snapshot of the social network among all the birds," explained Dr Culina. "By performing the same procedure many times over winter, we can track how relationships and social networks change over time."

Capturing data between 2007 and 2014, the team acquired 6,743,553 feeder visits made by 3,198 different Great Tits. The researchers have now analysed this wealth of information to assess whether measures of the social environment  such as the number of acquaintances of the opposite sex, the strength of relationship with a future breeding partner and the gender balances  has an effect on the likelihood of a pair of birds divorcing after the initial breeding.

The results show that males with a high proportion of female acquaintances are less likely to divorce their partner between breeding seasons. Interestingly, the absolute number of female associates isn't important  just the ratio of females to males in the social group. The results also show that males are less likely to divorce if the strength of the association with their partner is higher than their association with other females, and if they are experienced breeders.

"Our results seems to suggest that males use divorce to correct for non-preferred partnership," Dr Culina continued. "They might not be able to breed with their preferred female, so they ended up simply breeding with a less preferred one  then in the next season, they move on to another partner."

Meanwhile, the team found that a female's social environment didn't have any influence on the probability of divorce. While it's difficult to say exactly why that's the case without further experiments, Dr Culina suggested that it might be down to the fact that females choose partners based on more than their friendship with a male: "In Great Tits, males hold territories. That means that females that divorce their males also change territory. We wonder if females might pay more attention to the territory they want to live in than the social dynamics of the group when it comes to changing partners."



Thursday, 8 October 2015

Watch out for Nuthatches

Watch out for Nuthatches

The British Trust for Ornithology has launched a new online tool with which householders can log and track garden bird sightings.

Autumn is always an interesting time of year for garden birders and up-to-date movements of birds into gardens can now be tracked, for the first time, using the new interactive Garden BirdWatch results pages. Developed by the British Trust for Ornithology (BTO), these tools show that Nuthatches, in particular, are taking refuge in gardens this autumn, showing their second-highest monthly peak in 20 years.

The average numbers of seed-eating bird species vary dramatically every year depending on the amount of natural food available in the wider countryside. The last two years have seen low numbers of many seed-eaters in gardens thanks to spectacular crops of seeds like Beech and Sitka Spruce.

This year, however, seems to be a different story. Many seed-eating birds are already being seen in surprisingly high numbers for early autumn, suggesting that the seed crops may be poor this year. The most exciting increase is that of Nuthatch which has already been reported from a quarter of BTO Garden BirdWatch gardens, the second highest reporting rate since the survey started in 1995. Coal Tit and Siskinare also using garden resources more this autumn, both having been seen in the highest average numbers since 2012.

We know all this thanks to the astounding amount of data collected by thousands of volunteer BTO Garden BirdWatchers over the last 20 years. Until recently only a fraction of it was available online but now, thanks to recent developments in technology, the BTO have been able to make more of it available in an interactive way. Now different species can be compared on the same graph, their distribution can be mapped and different charts can be downloaded for further use.

Clare Simm, from the Garden BirdWatch team, commented: "We are really excited about these new developments. These new results pages allow us to show in greater detail the data collected by our participants and to inform, in a new way, how gardens are used by birds and other wildlife. Gardens are extremely important habitats for wildlife and now we have a resource to reflect this."

To find out more about BTO Garden BirdWatch (GBW), including how to take part, please get in touch by emailing gbw@bto.org, telephoning 01842 750050, or write to GBW, BTO, The Nunnery, Thetford, Norfolk, IP24 2PU. More information can also be found at www.bto.org/gbw.

Thursday, 1 October 2015

Nightjar on ground among heather

Ripping times on precious landscape

In a museum, you rarely get to touch the rare and the beautiful. In partnership with Sussex Wildlife Trust, the Arun and Rother Connections (ARC) Project is inviting volunteers to get physical and rip bits off one of the UK's increasingly scarce and valuable habitats.

We're holding a "Mega Volunteer Day" at Graffham Common in West Sussex; a prime example of lowland heath. The event will run from 10 am until 3 pm on Saturday the 10th of October.


Work will focus on removing invasive rhododendron, pine and birch saplings which are threatening to transform the common into woodland, with devastating effect for the resident heathland wildlife.



"We've already lost 80% of our lowland heaths in the South East and Graffham is an important part of the remaining 20%," says ARC Volunteer Coordinator Kate Whitton. "Because of the losses, the sort of wildlife which depends on it is also threatened. Removing these woody plants will ensure nightjars, sand lizards and silver studded blue butterflies will be seen and enjoyed here by future generations."

A walk and talk around the reserve will be held in the afternoon focusing on the importance of heathland habitat and its associated wildlife.

Volunteers are invited to come along, see how the heathland restoration work is progressing and get stuck in themselves. Tools and gloves will be supplied and refreshments and cakes provided.

Kate added: "We welcome new volunteers to join our growing community of people restoring threatened heathland in West Sussex. It's all about having fun and enjoying nature as well as caring for it."

Jane Willmott the Living Landscape Officer for the Sussex Wildlife Trust said: "Graffham Common nature reserve heathland restoration has been an amazing journey. The major pine clearance is complete and we already have beautiful heather regrowth and 3 scarce heathland birds have returned to breed after many years absence; nightjars, woodlark and tree pipits. The next phase is beginning now and we need lots of help to keep the invasive plants at bay".



A mini-bus transfer to site can be arranged around the local area for people who don't have their own transport and all reasonable travel expenses will be reimbursed. To book or for more information, contact either Kate Whitton on 01273 775 333 / email kate.whitton@rspb.org.uk or Jane Willmott on 07557 162 406 / email (janewillmott@sussexwt.org.uk).