To determine the amount of time that wild reproducing American kestrels are exposed to electric fields and magnetic fields from power lines and to examine the behavior of captive kestrels exposed to electric fields and magnetic field similar to those from power lines.
For the first aim, wild pairs of kestrels were observed between 9 am and 4 pm. Time they spent in the wooden nest box (approximately 1 m below the power line) was determined. One pair of kestrels was observed during courtship (14 day long), six pairs during incubation and brood rearing (28 days each), and three pairs during the fledgling phase (10 days).
For the second aim, 56 pairs of American kestrels were randomly selected and the behavior was examined under different stages of reproduction: 1.) courtship (11 pairs control group, 9 pairs exposure group), 2.) incubation (10 pairs control group, 6 pairs exposure group) and 3.) brood rearing (4 pairs control group, 4 pairs exposure group).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
60 Hz
Exposure duration:
71% - 91% of 24 h/day (estimated due to observed time)
wild kestrels
|
|
|
Exposure 2:
60 Hz
Exposure duration:
21 h/day for 95 days
captive kestrels
|
|
| Frequency | 60 Hz |
|---|---|
| Type | |
| Exposure duration | 71% - 91% of 24 h/day (estimated due to observed time) |
| Additional info | wild kestrels |
| Exposure source |
|
|---|---|
| Distance between exposed object and exposure source | 1 m |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1.2 µT | - | - | - | - |
| electric field strength | 50 V/m | - | - | - | - |
| Frequency | 60 Hz |
|---|---|
| Type | |
| Exposure duration | 21 h/day for 95 days |
| Additional info | captive kestrels |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 10 kV/m | - | - | - | - |
| magnetic flux density | 30 µT | - | - | - | - |
Free-ranging American kestrels: Kestrels were exposed for 25% to 75% of the observed time. In a 24 hours-period, exposure of free living adult kestrels was estimated to range from 71% during courtship to 91% during incubation.
Captive American kestrels: During courtship, exposed female birds were significantly more active, more alert and perched on the roof more frequently compared to females from the control group. Exposed males were significantly more active than control males during courtship and incubation. During brood rearing, exposed females preened and rested significantly less often in comparison to the control group.
The authors conclude that exposure conditions of wild and captive American kestrels during the breeding saison were similar. The data indicate that exposure to electric fields and magnetic fields similar to those from power lines could influence the behavior of American kestrels.
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