Roosting birds can cause extensive and costly damage to urban infrastructure. Metronet civils maintenance asset manager Danny Mendes reports on some of the innovative strategies being used to keep pigeons out of London Underground, ranging from repellent gel to hawks.
Pigeons pose a continuous problem on London Underground's railway network, from roosting on bridge structures to creating hazardous and unsightly mess in public thoroughfares, stations and depots. Their acidic and unhygienic droppings can damage rail and station infrastructure by causing paintwork and steel to deteriorate, in some cases leading to seizure of bridge bearings and failure of equipment.
Metronet, the company responsible for revitalising around two thirds of the network under a public-private partnership, uses a wide range of methods deter pigeons – ranging from traditional netting and spikes to more innovative solutions such as repellent gel and hawks.
One of the biggest problem areas is on bridges, particularly in the open and shallow sub-surface sections. On a typical double track steel underbridge, the company would spend around £25 000 on installing a good quality anti-pigeon system, and this normally needs replacement after 15 years. There are approximately 800 bridges over roads and around 10% of these have construction details that are favoured by roosting pigeons.
Netting, spikes and slopes
Pigeons are feral creatures and move from bridge to bridge depending on feeding and nesting opportunities. Control solutions need to ensure that the birds are prevented from roosting on the structure but without them getting trapped.
Bridge arches are a particular favourite for pigeons and placing mesh or netting underneath is one method to deter them. However this has to be removed before maintenance work and painting can be carried out and can also result in pigeons becoming trapped.
One of Metronet's many short-term solutions to reducing maintenance costs caused by pigeon damage is to make weekly visits to depots with a trained Harris hawk
One of Metronet's many short-term solutions to reducing maintenance costs caused by pigeon damage is to make weekly visits to depots with a trained Harris hawk
Spikes made of plastic are an alternative as they make it difficult for pigeons to land yet do not cause any harm. They are usually applied to narrow ledges and can be cut to form different shapes according to the structure of the bridge. For wider ledges, the most successful mitigation process to date has been the installation of sloped units to eliminate level perching positions.
Preventative measures also need to be maintained on a regular basis as they are frequently damaged by vehicles or persons wishing to access the structure, legitimate or otherwise. Indeed, installation costs can be a fraction of maintenance costs in some cases.
Legal obligation of owners
The London Boroughs Association has stated it would save a £1 million cleaning bill if pigeons were stopped from roosting on bridges. As a result, legislation has been introduced recently which places the onus on bridge owners to control pigeons nesting over footpaths and pavements.
But it is not just bridges that attract pigeons – the nooks and crannies in stations also make perfect nesting spots. The Control of Pigeons on Premises is relatively well defined in law and Metronet's public-private partnership contract also spells out the need for a pigeon-free, dropping-free ambience in stations.
Again netting and spikes are used extensively, with netting mainly used below canopies together with spikes in isolated areas. However, Metronet is also trying out a new repellent gel applied to ledges, which is proving reasonably successful.
Fighting birds with birds
Pigeons are also habitual visitors to rolling stock depots, where they nest in both the buildings and equipment. Metronet is now using a hawk to deter hundreds of pigeons from roosting and nesting at three of the biggest sub-surface depots – Hammersmith, Neasden and Ealing Common.
Every week a licensed trained Harris hawk is taken to the depots by a pest control company. The operative or falconer walks around the depots while the hawk flies above. The hawk is able to spot all hiding pigeons and scare them out of the area.
However, all of the measures currently being used are considered to be short term. In the long term it is better to design structures which discourage congregation of pigeons by eliminating horizontal ledges that allow them to roost.
FOR FURTHER INFORMATION CONTACT, Danny Mendes, TEL +44 (0)20 7121 4040, EMAIL danny.mendes@trans4m.co.uk
