Modifiers matching passerine:

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

Simple categories matching upland:

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