Modifiers matching passerine:

• passerine,
• migrant,
• insectivorous,
• exotic,
• small,
• interesting,
• breeding,
• smaller,
• european,
• upland,

Simple categories matching upland:

• bird,
• passerine,
• cover,
• game,
• space,
• shrub,
• feature,
• species,
• community,
• mammal,
• site,
• crop,
• development,
• area,
• wader,
• location,
• raptor,
• vegetation,
• grassland,