Effects of electromagnetic fields on photophasic circulating melatonin levels in American kestrels.

Abstract

Birds reproduce within electromagnetic fields (EMFs) from transmission lines. Melatonin influences physiologic and behavioral processes that are critical to survival, and melatonin has been equivocally suppressed by EMFs in mammalian species. We examined whether EMFs affect photophasic plasma melatonin in reproducing adult and fledgling American kestrels (Falco sparverius), and whether melatonin was correlated with body mass to explain previously reported results. Captive kestrel pairs were bred under control or EMF conditions for one (short-term) or two (long-term) breeding seasons. EMF exposure had an overall effect on plasma melatonin in male kestrels, with plasma levels suppressed at 42 days and elevated at 70 days of EMF exposure. The similarity in melatonin levels between EMF males at 42 days and controls at 70 days suggests a seasonal phase-shift of the melatonin profile caused by EMF exposure. Melatonin was also suppressed in long-term fledglings, but not in short-term fledglings or adult females. Melatonin levels in adult males were higher than in adult females, possibly explaining the sexually dimorphic response to EMFs. Melatonin and body mass were not associated in American kestrels. It is likely that the results are relevant to wild raptors nesting within EMFs.

AI evidence extraction

Main findings

EMF exposure affected plasma melatonin in male kestrels, with suppression at 42 days and elevation at 70 days of exposure, suggesting a seasonal phase-shift in the melatonin profile. Melatonin was suppressed in long-term fledglings but not in short-term fledglings or adult females. Melatonin and body mass were not associated.

Outcomes measured

• Photophasic plasma melatonin levels
• Body mass (association with melatonin)

Limitations

• Frequency and field strength/exposure metrics not reported in the abstract
• Sample size not reported in the abstract
• Captive study; generalizability to wild birds not directly tested

Suggested hubs

• occupational-exposure (0.2)
  Study concerns EMFs from transmission lines; relevant to environments near power infrastructure (not explicitly occupational).

{
    "study_type": "animal",
    "exposure": {
        "band": null,
        "source": "transmission lines (EMFs)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "42 days and 70 days; short-term (one breeding season) and long-term (two breeding seasons)"
    },
    "population": "Reproducing adult and fledgling American kestrels (Falco sparverius) in captivity",
    "sample_size": null,
    "outcomes": [
        "Photophasic plasma melatonin levels",
        "Body mass (association with melatonin)"
    ],
    "main_findings": "EMF exposure affected plasma melatonin in male kestrels, with suppression at 42 days and elevation at 70 days of exposure, suggesting a seasonal phase-shift in the melatonin profile. Melatonin was suppressed in long-term fledglings but not in short-term fledglings or adult females. Melatonin and body mass were not associated.",
    "effect_direction": "mixed",
    "limitations": [
        "Frequency and field strength/exposure metrics not reported in the abstract",
        "Sample size not reported in the abstract",
        "Captive study; generalizability to wild birds not directly tested"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "electromagnetic fields",
        "transmission lines",
        "melatonin",
        "photophase",
        "American kestrel",
        "Falco sparverius",
        "seasonal phase-shift",
        "sex differences",
        "fledglings"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "Study concerns EMFs from transmission lines; relevant to environments near power infrastructure (not explicitly occupational)."
        }
    ]
}

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