Effects of electromagnetic fields on the reproductive success of American kestrels.

Physiological and biochemical zoology : PBZ · 2000 · Mixed · Low evidence

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MixedLow evidencePaper 5354

Study snapshot

PublicationPhysiological and biochemical zoology : PBZ · 2000

Study typeanimal

Reported directionMixed

Evidence ratingLow

Abstract

Reduced reproductive success of birds nesting near power lines has been documented but never directly attributed to electromagnetic fields (EMFs). Laboratory studies have identified EMF effects on embryonic development, but reproductive success of wild birds is dependent on additional factors, including fertility, egg size, hatching, and fledging success. We tested whether EMFs affect reproductive success of birds. Captive American kestrels (Falco sparverius) were bred for one season per year for 2 yr under either controlled or EMF conditions. EMF exposure was equivalent to that experienced by wild reproducing kestrels and was weakly associated with reduced egg laying in 1 yr only. In both years fertility was higher, but hatching success was lower in EMF pairs than control pairs. Fledging success was higher in EMF pairs than control pairs in 1995 only. Egg composition and embryonic development were examined in 1 yr only, but hatchlings were measured in both years. EMF eggs were larger, with more yolk, albumen, and water, but had thinner egg shells than control eggs. Late-term EMF embryos were larger and longer than control embryos, although hatchlings were similar in body mass and size. EMF exposure affected reproductive success of kestrels, increasing fertility, egg size, embryonic development, and fledging success but reducing hatching success.

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeanimal

Effect directionmixed

PopulationCaptive American kestrels (Falco sparverius)

Sample sizeNot supplied

Exposurebred for one season per year for 2 years under EMF vs controlled conditions

Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

EMF exposure equivalent to that experienced by wild kestrels was weakly associated with reduced egg laying in 1 year only. Across both years, fertility was higher but hatching success was lower in EMF pairs than controls; fledging success was higher in EMF pairs in 1995 only. EMF eggs were larger with more yolk/albumen/water but thinner shells; late-term embryos were larger/longer, while hatchlings were similar in mass and size.

Outcomes measured

egg laying
fertility
egg size
hatching success
fledging success
egg composition (yolk, albumen, water)
egg shell thickness
embryonic development (size/length)
hatchling body mass and size

Limitations

Frequency and exposure metrics (e.g., field strength, SAR) not reported in the abstract
Egg composition and embryonic development assessed in only 1 year
Some outcomes differed by year (e.g., egg laying reduction in 1 year only; fledging success higher in 1995 only)
Sample size not provided in the abstract

View raw extracted JSON

{
  "study_type": "animal",
  "exposure": {
    "band": null,
    "source": "power lines (simulated EMF exposure equivalent to wild kestrels near power lines)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "bred for one season per year for 2 years under EMF vs controlled conditions"
  },
  "population": "Captive American kestrels (Falco sparverius)",
  "sample_size": null,
  "outcomes": [
    "egg laying",
    "fertility",
    "egg size",
    "hatching success",
    "fledging success",
    "egg composition (yolk, albumen, water)",
    "egg shell thickness",
    "embryonic development (size/length)",
    "hatchling body mass and size"
  ],
  "main_findings": "EMF exposure equivalent to that experienced by wild kestrels was weakly associated with reduced egg laying in 1 year only. Across both years, fertility was higher but hatching success was lower in EMF pairs than controls; fledging success was higher in EMF pairs in 1995 only. EMF eggs were larger with more yolk/albumen/water but thinner shells; late-term embryos were larger/longer, while hatchlings were similar in mass and size.",
  "effect_direction": "mixed",
  "limitations": [
    "Frequency and exposure metrics (e.g., field strength, SAR) not reported in the abstract",
    "Egg composition and embryonic development assessed in only 1 year",
    "Some outcomes differed by year (e.g., egg laying reduction in 1 year only; fledging success higher in 1995 only)",
    "Sample size not provided in the abstract"
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "electromagnetic fields",
    "power lines",
    "birds",
    "American kestrel",
    "reproductive success",
    "fertility",
    "hatching success",
    "fledging success",
    "egg size",
    "embryonic development"
  ],
  "suggested_hubs": [
    {
      "slug": "power-lines-elf",
      "weight": 0.78,
      "reason": "Study motivated by reduced bird reproductive success near power lines and uses EMF exposure equivalent to that experienced near power lines."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1086/316726
PubMed: 10685907

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