the surrounding areas. The power lines are used as vantage and singing points by
the corn bunting, in addition to the spotless starling. In the case of passages and
bridges, the only note-worthy use was by the rock dove and the rock sparrow; both
species rest and nest in holes within these structures. The ballast is only used by the
crested lark, while the catenary poles are occupied as vantage points by the common magpie. It is noteworthy that during the monitoring presented in this chapter,
it was discovered that these poles act as pitfall traps that cause the death of birds
that fall inside (Malo et al. 2016). The spotless starling was the most affected
species by this, but magpies and kestrels also suffered this fate. Finally, although the
fences are used by many species, their use is only remarkable in the case of the
house sparrow and European stonechat (Saxicola torquatus).
In conclusion, the HSR provides new structural elements for birds, which are
used in accordance with the particular requirements of the species (Morelli et al.
2014). However, among the species that use these elements, some were found to
present their maximum densities in close proximity to the railway (common linnet,
house sparrow). More frequently, however, species were repelled by the railway
(spotless starling, rock dove, crested lark). Therefore, the direct expectation that
species that make an active use of the new opportunities provided by the HSR
would increase their densities in proximity to the railway (Benítez-López et al.
2010), and in the area as a whole, was not fully met.
Bird Flight Over the Railway
In a sequential approach to the presentation of findings in the previous sections, to
understand the potential magnitude of the HSR impact on birds, it is key to know to
what extent flying birds face the risk of being overrun by circulating trains.
Mortality from roadkill is one of the most serious direct impacts of operating
transportation infrastructures (Loss et al. 2014). The potential relevance of the HSR
is conditioned by the fact that the great speed of the trains, in most cases, precludes
birds from avoiding train collisions (DeVault et al. 2015). If birds could fully avoid
running trains by flying above their height, the railway would remain responsible
only for effects on habitats and for increases in energy expenditure by individuals
that cross it in flight.
The collision risk area associated with the HSR corresponds basically to the
section framed by the catenary and the rails. In a simplified view, for twin tracks, it
corresponds to a rectangle with an 8 m-wide base that is 5.3 m high (height of the
power wire) where the trains run. Additionally, it is hazardous for birds to fly above
the train collision risk area where they may come in contact with the catenary,
suspenders, power wire, feeder, earth cable, and tensors (5.3–8.5 m above the
ground). Although there is a constant risk of collision with these elements even
when trains are not running, the risk of collision with the catenary may be increased
by the passage of trains due to the potential for turbulence generated by the moving
train to destabilize the normal flight of birds. Thus, it is reasonable to assume that
8 Cross-scale Changes in Bird Behavior Around …
125
the corn bunting, in addition to the spotless starling. In the case of passages and
bridges, the only note-worthy use was by the rock dove and the rock sparrow; both
species rest and nest in holes within these structures. The ballast is only used by the
crested lark, while the catenary poles are occupied as vantage points by the common magpie. It is noteworthy that during the monitoring presented in this chapter,
it was discovered that these poles act as pitfall traps that cause the death of birds
that fall inside (Malo et al. 2016). The spotless starling was the most affected
species by this, but magpies and kestrels also suffered this fate. Finally, although the
fences are used by many species, their use is only remarkable in the case of the
house sparrow and European stonechat (Saxicola torquatus).
In conclusion, the HSR provides new structural elements for birds, which are
used in accordance with the particular requirements of the species (Morelli et al.
2014). However, among the species that use these elements, some were found to
present their maximum densities in close proximity to the railway (common linnet,
house sparrow). More frequently, however, species were repelled by the railway
(spotless starling, rock dove, crested lark). Therefore, the direct expectation that
species that make an active use of the new opportunities provided by the HSR
would increase their densities in proximity to the railway (Benítez-López et al.
2010), and in the area as a whole, was not fully met.
Bird Flight Over the Railway
In a sequential approach to the presentation of findings in the previous sections, to
understand the potential magnitude of the HSR impact on birds, it is key to know to
what extent flying birds face the risk of being overrun by circulating trains.
Mortality from roadkill is one of the most serious direct impacts of operating
transportation infrastructures (Loss et al. 2014). The potential relevance of the HSR
is conditioned by the fact that the great speed of the trains, in most cases, precludes
birds from avoiding train collisions (DeVault et al. 2015). If birds could fully avoid
running trains by flying above their height, the railway would remain responsible
only for effects on habitats and for increases in energy expenditure by individuals
that cross it in flight.
The collision risk area associated with the HSR corresponds basically to the
section framed by the catenary and the rails. In a simplified view, for twin tracks, it
corresponds to a rectangle with an 8 m-wide base that is 5.3 m high (height of the
power wire) where the trains run. Additionally, it is hazardous for birds to fly above
the train collision risk area where they may come in contact with the catenary,
suspenders, power wire, feeder, earth cable, and tensors (5.3–8.5 m above the
ground). Although there is a constant risk of collision with these elements even
when trains are not running, the risk of collision with the catenary may be increased
by the passage of trains due to the potential for turbulence generated by the moving
train to destabilize the normal flight of birds. Thus, it is reasonable to assume that
8 Cross-scale Changes in Bird Behavior Around …
125