Key Notes on Seabird Threats and Conservation

Stressors Affecting Seabirds

  • Understanding Stressors
    • Inform the conservation efforts for seabird populations.
    • Key stressors include invasive species, fisheries, human exploitation, climate change, pollution, disease, and offshore renewable energy production.

Key Threats to Seabirds (Dias et al., 2019)

  • Threat Categories
    • Invasive Alien Species:
    • Example: Rats, Cats, and Mink resulted in considerable declines in seabird populations.
    • 127 bird species have gone extinct since 1600; 92% were island-dwelling species.
    • Bycatch in Fisheries:
    • Longline fisheries implicated in annual deaths of 160,000 – 320,000 seabirds.
    • Human Exploitation:
    • Direct hunting and usage of seabirds for oil, clothing, and sport.
    • Climate Change:
    • Affecting seabird survival through changing ecosystem dynamics and food shortages.
    • Pollution:
    • Plastic and chemical pollutants impact seabird health and reproductive success.
    • Diseases:
    • Increased susceptibility due to environmental stressors.
    • Offshore Renewable Energy Production:
    • Habitat changes and collisions with installations can disrupt populations.

Invasive Species Impact on Seabirds

  1. Types of Invasive Species:

    • Predators like rats and cats have devastating impacts on seabird nesting success.
    • Example Case:
      • Tristan albatrosses affected by house mice leading to population declines.

  2. Ecological Impact:

    • Seabirds adapted avoidance behavior leading them to nest in dense aggregations and offshore islands.
    • If these predator defenses are compromised, seabird populations face drastic reductions.

  3. Habitat Restoration Strategies:

    • Successful eradication efforts (like rats) lead to substantial increases in seabird populations.
    • Example: Rat eradication on islands led to regeneration from 4,306 pairs to 138,878 pairs due to successful breeding. (Carr et al., 2019)

Fisheries Threats to Seabirds

  • Bycatch in Longline Fisheries:

    • Bait attracts seabirds, leading to entanglement and drowning.

    • Affects albatrosses, petrels, and shearwaters significantly.

    • Mitigation Efforts:

    • Implementing night setting, streamer lines, underwater chutes, and weighting dying bait to decrease bycatch.

  • Set-net Bycatch:

    • Monofilament nets can capture thousands of diving seabirds without them seeing the hazard.
    • For example, Newfoundland sees up to 30,000 guillemots caught annually.

  • Prey Depletion and Competition:

    • Overfishing of forage fish leads to significant competition for seabirds.
    • Example: Increased fishing for anchovies resulted in increased foraging efforts by Peruvian Boobies.

Human Exploitation of Seabirds

  • Historical Context:

    • The Great Auk represents a case of human exploitation led to extinction in 1844; first protection laws emerged in 1553.

  • Current Exploitation Trends:

    • Puffins, Gannets, and Muttonbirds continue to face exploitation, with millions affected due to hunting.

  • Population Impacts:

    • Adult long-line mortality can lead to significant changes in population viability estimates, reducing lambda values considerably. (Hunter & Caswell, 2005)

Summary of Other Threats

  • Climate Change:

    • Alters habitat and resource availability impacting breeding success.

  • Pollution:

    • Negative effects on reproductive health due to habitat degradation.

  • Disease:

    • Increased outbreaks linked to environmental stress.

  • Offshore Renewables:

    • Present challenges in terms of habitat alteration and potential bird interactions with energy infrastructure.