Table 1. Hierarchical classification of threats to alpine birds.

1st level of threat	2nd level of threata
1. Residential and commercial development	1.1. Urbanization—increases in housing, commercial and industrial areas
2. Agriculture/silviculture	2.1. Forestry—Changes to management of forests, e.g., harvesting strategies (clear-felling vs. selective logging), understorey clearance
	2.2. Grazing—Increases in sheep or cattle densities (e.g., changes to sward structure, disturbance to ground nesters)
3. Natural system modifications	3.1. Abandonment—Changes derived from pastoral abandonment (e.g., scrub encroachment, forest succession, changes to sward structure)
	3.2. Climate Change—Direct and indirect impacts of climate change
	3.3. Fire—Human induced fire
4. Biological resource use	4.1. Hunting—Both licensed and illegal hunting (includes persecution, e.g., of raptors) and fishing
5. Human intrusion and disturbance	5.1. Leisure—Direct disturbance and/or habitat modification due to winter sports (including piste creation and management and off-piste skiing/free riding), walking, biking, birdwatching, rock climbing, scrambling, paragliding.
7. Energy production and mining	7.1. Mining—Presence of open-cast mines or quarries
	7.2. Energy—Developments in renewable energy such as wind turbines, hydroelectric power (e.g., effects on water flow and quality, effects on riverside habitats), solar power.

Notes.

^aNames of 2nd level threats given in italics are used as abbreviations for each threat in the text.