The London Wetland Centre (LWC) in Barnes is a jewel in the crown for London’s biodiversity. Every time I visit it, I cannot but help think how privileged Londoners are to have such a fantastic nature reserve. I was on a guided walk in November, organised by the London Bird Club (LBC), which is a section of the London Natural History Society. It organises a number of birdwatching walks to London’s sites and in recent years has begun to organise no less than four nature walks, one for each season at the LWC. The LWC is one of the few sites which meet the London Bird Club’s criteria for staging a guided bird watching walk in each season. The LBC has three criteria. Firstly, the site must be sufficiently wildlife-rich or biodiverse. Secondly, it must have good visitor facilities. The LWC excels in the first two criteria.
The site is intensively managed as a wetland with rotational cropping of its reedbeds, meadows and scrub. Although primarily a wetland, it has a number of different habitats which make it very species-rich. In terms of visitor facilities, it is best in class, as is generally the case with many of the sites in the UK managed by the Wildfowl and Wetland Trust (WWT). The visitor centre has a large café with a range of hot and cold food and drinks. There is a large shop with the usual fare for visitors and includes one of the best wildlife bookshops in the UK. For birdwatchers and photographers, there are a large number of hides, many of which are placed such that fairly close views may be had of resident and migrant birds and other wildlife. It also has a captive collection of water birds arranged by habitats for the general public.
On a cold winter’s day in November, I found myself co-leading a London Bird Club Walk at the LWC with Michael Howard and Jason Anderson. We began with an overview of the history of the site inside a tall structure called the Observatory. This is a large, heated, two-storey building with a floor-to-ceiling glass front. It is even available for hire for small functions by corporates and wedding parties. It is also a comfortable bird watching hide. It even has heating in winter. From the hide, Jason found a Bittern and the group enjoyed views through a birding telescope. The Bittern may have been an arrival from the Netherlands. Migrants had swelled the numbers of waterfowl and we observed Gadwall and Shoveler. In the distance were gulls.
We had a number of beginners who had come for the LBC walk. It was a cold day and as there was no need to turn the birdwatching walk into an endurance trial, I informed the group we can spend more time in the hides which are warmer and less exposed. With two experienced birdwatchers co-leading with me it also allowed an opportunity to coach the beginners on the identification of gulls that can don a bewildering array of plumages. Gulls are of particular interest to birdwatchers as some species look alike and need careful scrutiny to identify them to species level. An added level of complexity is the multiple plumage changes. Some species of gull such as the Black-headed Gull, a common bird in Britain, attains its adult plumage in the second winter. Other species of gulls may need a third or fourth winter to reach adult plumage. As a general rule, the larger the gull the more years it takes to reach maturity.
From the comfort of one of the hides, we explained the process of moult to the beginners in the group using the Black-headed Gull as a case study. A few weeks after they are born, the chicks shed their fluffy plumage and acquire a set of brownish feathers which is the juvenile plumage which they will wear when they start flying. In Autumn, gulls will undergo a complete moult where they renew all of the feathers. i.e. head and body feathers as well as the wing and tail feathers. However, in the case of juveniles who are in their first year, this post-juvenile moult is only a partial moult. They will replace just the head and body feathers. The juvenile Black-headed Gulls moult into adult feathers on the head and body. However, they retain the juvenile feathers on the wings and tail. As a result in a winter month like November, we were able to see what is known as two age classes or age group.
There was a mix of adult and first-winter Black-headed Gulls. Just looking at their heads, they look similar. However, the birds in their first winter could be easily recognised from the brown feathers on the wings. They also had a diagnostic dark terminal band on the juvenile tail feathers. Although, the rest of the body was adult-like, on careful inspection it could be seen that the first winter birds did not have as deep a red on the bill and the legs as the adult birds that would be in their second winter or older. Black-headed Gulls can live for over 20 years. By looking at plumage alone it is not possible to age them once they have reached full adult plumage by their second winter. The age records of gulls are established from birds that have been ringed. The traditional method is to recover rings from dead birds or to capture and release live birds having noted the unique serial number on a ring. A dedicated band of gull watchers also read the unique serial numbers on rings using birding telescopes and upload the date and location online portals to enable a photographic ‘capture and release’ system for ringed gulls.
In Spring, gulls will undertake a Spring moult which is a complete moult replacing all of their feathers. Young gulls which were in their first winter will now shed their head and body feathers and assume the same chocolate brown hoods of adult birds. Their wings and tail feathers will also look exactly like that of the adult birds that have replaced their wing and tail feathers with a fresh set. The legs and bill colour of the young birds will also turn a brighter red as with the adults. Birds in their first summer are now indistinguishable from older adults as they are all now in adult summer plumage. But now the adult summers will be joined by birds in juveniles so that once again there are two age classes of birds.
We spent some time studying the different Black-headed Gulls and gave time for the beginners to practice telling apart the first winters from the adults. We also studied the Common Gulls which attain their adult plumage with the third winter. There were also plenty of opportunities to examine Herring Gulls and Lesser Black-backed Gulls which attain adult plumage in their fourth winter. As with the Black-headed Gulls, in the summer following the winter in which the birds attain their first adult winter plumage, the young birds after a Spring moult, will attain their first adult summer plumage. At that point, the young birds in their first adult summer plumage will be indistinguishable from older birds that have spent many previous summers in full adult plumage.
With the three-year and four-year gulls, in winter, one will see more age groups. Thus in winter, with Common Gulls, there will be first winter, second winter and adult winter gulls. With the Herring and Lesser Black-backed Gulls, there will also be another age group, the third winter gulls. We spent more time examining the other gulls plus the ducks and woodland birds before heading back to the café for hot drinks and food.
Whether I am leading an LBC walk or not, one of the books I find useful to have in my day pack or jacket is The Birdwatchers Guide to Britain and Europe by Peter Hayman by Mitchell Beazley. It is affordable, lightweight and compact with superb identification text and illustrations by Peter Hayman one of the pre-eminent ornithological artists in the world. The newer editions are co-authored with Rob Hume an expert on bird identification. I cannot think of a bird field guide which packs in so much expertise for its price and weight and it has remained a standard setter for decades. The gulls are very well covered in ‘Hayman book’ with the plumage for different age groups illustrated. Those who are keen to get into gulls will also like The Collins Bird Guide by Lars Svensson, Killian Mullarney and Dan Zetterstrom which is published by Collins. A delightful book to help beginners grapple with advanced ID topics is Birds ID Insights: Identifying the More Difficult Birds of Britain with text by Dominic Couzens and illustrations David Nurney which is published by Bloomsbury. A similar theme is The Helm Guide to Bird Identification: An in-depth look at confusion species by Keith Vinicombe, Alan Harris, and Laurel Tucker, also published by Bloomsbury. For those who prefer a photographic guide, an excellent book is Britain’s Birds: An identification guide to the birds of Great Britain and Ireland by Rob Hume et. al. published by WildGuides. Once you have become a larophile there are a small number of family monographs on gulls published by publishers such as Bloomsbury and Princeton University Press.
Undoubtedly there is now a wide variety of affordable literature for anyone who wants to head to a local river or waterbody in their local park and would like to self-learn how to age gulls. One of the best ways to learn of course is to join the guided walks led by a local natural history society or bird club. Not only does this accelerate the learning process but it also brings in the social interaction (subject to prevailing guidance) the importance we appreciate now even more with the recent pandemic years that saw the introduction of restrictions on social interaction.
A number of groups in London organise a range of bird-watching and other nature walks as well as day trips by coach or by using public transport to sites further afield from London. Three groups which are especially suited for residents and visitors in Central London are the London Natural History Society, Marylebone Birdwatching Society and the RSPB Central London Local Group.
For visiting nature reserves in London, see also the websites of the London Wildlife Trust and London Wetland Centre. For nature based activities for children and adults in a Central London Park, see the website of the Holland Park Ecology Centre.