A study of more than 3,500 poultry keepers in the Netherlands reveals a highly diverse and largely under-characterised population of backyard and small-scale flocks. With 41% of respondents allowing birds to free-range and mixed-species flocks common in some settings, researchers say these holdings should be more explicitly included in avian influenza surveillance and One Health risk assessments.
Small-scale and backyard poultry have become increasingly common in many high-income countries, but they remain poorly documented compared with commercial farms. This is particularly relevant for avian influenza surveillance because backyard birds may live at the interface between wild birds, domestic poultry and humans.
Researchers therefore conducted the first nationwide survey describing small-scale and backyard poultry holdings across the Netherlands, collecting data between March and September 2025. A total of 3,525 poultry keepers were included in the analysis after exclusions.
Backyard flocks dominate the sector
The overwhelming majority of respondents (3,336 out of 3,525 ) identified themselves as backyard flock owners.
Other holding types included:
110 petting zoos or care farms
42 ornamental poultry breeders
37 small-scale community farms.
Backyard flocks were generally small, with a median of five birds, and 83.8% kept no more than ten birds.
By comparison, median flock sizes reached:
23 birds in petting and care farms
48 birds among breeders
60 birds in small-scale farms.
The motivations for keeping poultry also varied considerably.
Across all respondents, 95% reported keeping birds as a hobby or for companionship, while 69.7% kept them for egg production.
Petting and care farms were more strongly associated with educational and community purposes, whereas small-scale farmers more frequently cited egg production and supplementary income.
Chickens predominate, but mixed flocks are common
Chickens were by far the most commonly kept birds. Among backyard flock owners, 86.7% kept chickens only. However, mixed-species flocks were much more common in some other types of holdings. Around 60% of petting and care farms kept both Galliformes and Anseriformes, including chickens together with ducks, geese or swans.
Mixed Galliformes–Anseriformes flocks were also reported by 26.2% of breeders and 21.6% of small-scale farmers.
This composition is particularly relevant for avian influenza. Wild and domestic Anseriformes can carry influenza A viruses with few or no clinical signs and may shed virus through faeces, saliva and respiratory secretions. Keeping ducks or geese in close contact with chickens could therefore facilitate introduction of avian influenza viruses into susceptible gallinaceous flocks.
Among respondents keeping several taxonomic groups, 35% of backyard owners, 44% of petting and care farms and 45% of breeders reported housing or feeding Galliformes and Anseriformes together.
41% of poultry keepers reported free-range access
Housing practices also highlighted potential pathways for contact with wildlife. The most common arrangement combined an enclosed night shelter with access to an outdoor coop or netted area. However, 41% of all respondents (1,444 of 3,525 holdings) reported free-range management, meaning birds could roam freely outside without confinement to a coop or netted enclosure. Outdoor access may increase opportunities for direct or indirect contact with wild birds, particularly waterfowl, which are important reservoirs of avian influenza viruses.
The researchers stress, however, that the study did not measure infection rates or quantify the actual probability of avian influenza introduction into individual backyard flocks.
A largely invisible poultry population
One of the central problems identified by the study is regulatory. In the Netherlands, poultry owners are generally only required to register their birds when they keep more than 250 animals, or when poultry products such as eggs are sold commercially.
Smaller non-commercial backyard flocks are therefore largely absent from official registration systems. The number of backyard poultry keepers in the country had previously been estimated at more than 100,000, collectively keeping over one million birds, although that estimate dates back to 2004. This creates a potential gap in surveillance.
The Netherlands combines a high density of commercial poultry, a dense human population and large populations of migratory waterbirds using the East Atlantic Flyway. Small poultry holdings scattered across rural, suburban and even urban environments may therefore form part of a much broader wildlife–livestock–human interface.
Not only a rural phenomenon
The survey also showed that backyard poultry keeping is not confined to rural regions. Overall, 46.4% of respondents lived in rural areas, 37.4% in suburban areas and 13.3% in urban areas. Petting and care farms were particularly notable, with 54.5% located in urban areas.
This broad spatial distribution means that potential contact between poultry, wildlife and people may occur across very different environments.
A missing component of surveillance
The study does not show that backyard poultry are driving avian influenza outbreaks in the Netherlands. Instead, it highlights how little is known about a sector that may be relevant to disease surveillance. Small flocks can combine several characteristics potentially important for pathogen transmission: outdoor access, interaction with wild birds, mixed bird species, close human contact and, in many cases, absence from formal registration systems.
The authors argue that backyard and small-scale poultry should therefore be more explicitly incorporated into surveillance, zoonotic risk assessment and disease-prevention strategies. Future work will need to quantify actual wild bird–poultry contacts, assess biosecurity practices and determine which types of holdings are most likely to experience pathogen spillover.
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