Most poultry will avoid eating poisonous plants due to their bitter taste but chickens are at risk from laburnum seeds, potato sprouts, black nightshade, henbane, most irises, privet, rhubarb leaves, rhododendron, oleander, yew, castor bean, sweet pea, rapeseed, corn cockle, clematis, common St. John’s Wort, meadow buttercup, vetch, ragwort and some fungi.
Blue-green algae is quickly fatal, so water containers should be kept clean, especially in hot weather and access to stagnant water should be prevented.
Phenol-based disinfectants are toxic, as is zinc from rusty galvanised drinkers.
Access to lead (old paint) should be prevented.