Modifiers matching passerine:

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

Simple categories matching upland:

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