Professional Pest Controller issue 92

30 August 2018

PESTWATCH: Secondary infestations from birds

Technical | PPC92 September 2018

Continuing PPC’s round of in-depth PestWatch features, Field Officer Natalie Bungay inspects birds’ homes and finds some unwelcome guests within them.

Secondary infestations from birds

When we think about birds nesting or roosting around homes or businesses, we usually think of problems such as noise complaints, bad odours, building damage, and public health concerns. An area of concern rarely considered by the unsuspecting building tenant is secondary pest insect infestations.

Secondary pest insect infestations (SPII) can be wide-ranging and numerous when a bird nesting site is nearby. With an SPII your client gets even more nuisance, potential fabrics and fibres damage, and an additional expense to deal with the second pest issue.

When birds move into a nesting location and begin to build homes for their breeding season, they bring with them many attractive sources of food for various insects. The birds themselves can be tasty blood meals. Their feathers and nesting material can provide an appetising food source as well as their droppings harbouring a few mould-loving invertebrates! This pest activity can occur from nests within confined spaces, such as loft spaces and cavities, as well as when nesting outside on a ledge or flat roof.

The invertebrate pests can and will migrate away from nests which is when the unsuspecting human below starts to notice an additional problem.

Variegated carpet beetles - Anthrenus Verbasci 

Variegated carpet beetles


Variegated carpet beetles are a common sight in the UK, especially around bird’s nests. The larvae, AKA ‘woolly bears’, feeds on fabrics, carpets, clothing, fur and stuffed specimens and sometimes the heads of sweeping brushes and mops if it’s made of natural fibres.


Up to 100 eggs are laid singly on larval food (such as a carpet). In ten days to one month, they’ll hatch into the larvae form - the ‘woolly bear’. After five moults, over a few months, they develop in the pupae stage. It takes them ten days then to mature into adults - which are active flyers.


The thorax and wing cases of the adult can be very beautiful with a mixture of orange, white, pale yellow, black and brown scales, in an irregular W pattern.

The adults are harmless feeding mostly on pollen and nectar. When these adults fully emerge from the pupae (usually in spring), they will head straight for a pollen/nectar source which is why we can often find them on window ledges struggling to escape the house.

Variegated carpet beetle wooley bear

Controlling carpet beetles

The principles of controlling this secondary pest are the same for most insect pests associated with birds’ nests. Remove all nesting and related material from the cavity, attic and outside ledges. Then the regular eradication steps can be taken in the property where the adults and larvae may have migrated.

A thorough vacuum can assist in physically removing debris and larvae from cracks and crevices. A residual insecticide should then be used focusing on cracks and crevices. As always, desiccant dusts can be very useful also.

Whatever insect or mite pest it may be that you come across, always ensure you identify its source as this will always be the most effective initial control point. In the event of not being able to access the nest, explain to the customer that the issue may not completely resolve itself until the birds have left the nest, the entrance has been sealed off (to prevent future ingress), and the remaining insects have either contacted a pesticide or succumbed to natural death.

Bird mites - Dermanyssus Gallinae

Bird mites


You typically find them around birds nests and poultry units. They live in the nest or structure during the day and move towards the bird at night to feed.


Up to seven eggs are laid in or around a birds nest. The larvae emerge from the egg with only six legs. In two days they moult. The nymphs have eight legs and start feeding on blood. In two moults they become the adult.


Their colour will vary depending on how recently they’ve fed. Well-fed: dark red to almost black. Starved: very pale.

Did you know - Bird Mites

Bird mites are parasitic arthropods in the acari (tick/spider) family that feed on living organisms. It is the female mite that needs a blood meal to reproduce viable eggs. They are attracted to mammals by receptors for moisture, heat and CO2, and they often bite humans when their original food source has gone – like when the young birds leave the nest.

Parasite misery

These little critters can quickly multiply into thousands, leaving the afflicted person feeling overwhelmed. If you have dealt with a parasite infestation for any length of time, you’ll soon come to realise that the mental anguish is often more difficult than the solid torment. The relentless biting, itching, crawling sensation and lack of sleep are the physical symptoms that can propagate a whole host of secondary mental health issues. If you’re dealing with any parasite infestation, it’s important to be compassionate with the client.

Once a home is heavily infested, they can be very difficult to eradicate fully. Mites are common outdoors in bird nests as well as in intensive poultry units. The incidence of these in domestic premises, as a result of their migration from bird nests in the eaves, is quite common but usually very localised. The situation becomes a little more common in urban areas, and this is generally due to pigeons nesting outside on ledges.


To overcome these issues, it’s essential to remove the nesting site. Without doing this, the issue will likely rage on regardless of any chemical treatment.

In poultry units, where you can’t just remove a nest, you’ll need a combination of regular housekeeping and good hygiene practices. You’ll need to inject insecticides into all cracks and crevices around the cages and surfaces that could have been contaminated by the mites.

The birds themselves should be seen by a veterinary professional so they can be suitably treated.

In areas other than farming situations (domestic and commercial buildings), when the nest has been removed, use conventional insecticides in cracks and crevices and surfaces that they come into contact with. Make sure the insecticide is approved for use against these mites.

Always ensure that you rotate your insecticides and consider using desiccants containing diatomaceous earth.

Other bird SPIIs

Birds nests can attract flies

Birds nests have many blood-feeding parasites that live in their nests and can bite humans if they migrate away from the nest area, this may be due to a nest that is vacated by the bird or natural distribution of the insect. These biting insects include the Martin bug (Oeciacus hirundinis) and the pigeon flea (Ceratophyllus columbae).

Also, there can be a wide variety of other insects that appear due to the presence of feathers, nesting material and droppings. Many of the insects named below will move on to infest fabrics, stored food, etc. To name a few of the more common insects, we may come across spider beetles (Ptinus spp); yellow/lesser mealworm beetles (Tenebrio molitor and Alphitobus diaperinus); the lesser housefly (Fannia canicularis); the white-shouldered house moth (Endrosis sarcitrella); and the fur beetle (Attagenus pellio).

In addition, when adult birds or young chicks die inside a building they become a significant source to carrion eaters such as bluebottles, greenbottles and even flesh flies.

Want to know more about a particular pest?

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Natalie and DeeDee Ward-Thompson and Natalie Bungay
BPCA Technical Team

September 2018  |  PPC92

Source: PPC92

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