Seagulls with black heads are simply a color variant of the common gull species. They exhibit a genetic condition known as melanism which causes increased black pigmentation. While strikingly different in appearance, black-headed gulls are the same species as their lighter counterparts.
What Causes Black Heads in Seagulls?
The black heads seen in some seagull populations are caused by increased melanin pigmentation. Melanin is the natural pigment that gives feathers, hair, and skin their color. An overproduction of melanin leads to darker coloration.
There are a few possible reasons for increased melanism in seagulls:
- Genetic mutation – A random mutation in a gene involved in melanin production can cause increased black pigment.
- Evolutionary adaptation – In some environments, black coloration may help seagulls blend into their surroundings better, providing an evolutionary advantage.
- Diet – Access to foods rich in amino acids involved in melanin synthesis may lead to more black pigmentation.
Regardless of the exact cause, the end result is seagulls with striking black heads rather than the usual white or gray plumage.
Are Black-Headed Seagulls a Distinct Species?
Despite their unique appearance, black-headed seagulls are not considered a separate species from normally colored gulls. They are simply color variants.
Some common gull species with black-headed individuals include:
- European Herring Gull
- Lesser Black-backed Gull
- Great Black-backed Gull
- Kelp Gull
These gulls interbreed freely with normally plumaged individuals of the same species. The black head is caused solely by abnormal melanin levels, not any inherent genetic differences.
Differences Between Black-Headed and Normal Seagulls
While their plumage differs, black-headed seagulls are essentially identical to normally-colored gulls of the same species in all other respects:
- Size and dimensions – Black-headed gulls have the same body size and proportions.
- Behavior – No differences in feeding, breeding, or social behaviors are seen between color variants.
- Diet – They have identical dietary preferences to normally-colored counterparts.
- Genetics – Aside from melanin levels, genetics are the same as normally-colored gulls.
- Reproduction – Black-headed gulls successfully interbreed with lighter color morphs of the same species.
The only consistent difference is the extent of black pigmentation in the plumage. Even the bills and legs remain similarly colored.
Population Share of Black-Headed Gulls
Black-headed gulls make up a relatively small portion of overall gull populations. Their numbers vary by region and species:
| Species | Total Population | Black-Headed Percentage |
|---|---|---|
| European Herring Gull | 5.4 million pairs | 1-8% |
| Great Black-backed Gull | 370,000-580,000 pairs | 10-15% |
| Kelp Gull | 110,000 pairs | 5-10% |
As these numbers show, the black-headed variants occur in small but consistent proportions in many gull species worldwide. Their numbers appear stable, with the black-headed morphs continuing to persist as part of overall gull diversity.
Are Black-Headed Gulls Rare or Endangered?
Although they make up a relatively small percentage of total birds, black-headed gulls are not considered rare or endangered. Their populations appear to be stable without risk of disappearing.
There are a few reasons why melanistic gulls remain secure despite their lower numbers:
- The trait persists through steady genetic inheritance, without signs of decline.
- Black-headed gulls successfully breed with normal birds, maintaining genetic diversity.
- They exhibit identical survival ability and habitat use compared to lighter gulls.
- Legal protections and conservation efforts apply equally to both color variants where implemented.
Tracking of population trends in regions like the UK has not shown evidence of decreasing black-headed gull numbers. As long as supportive environmental conditions continue, they are expected to endure as part of natural gull diversity.
What Causes Black Spots in Seagulls?
Some individual seagulls may exhibit scattered black spots or streaks in their plumage in addition to or instead of a full black head. These markings are also caused by increased localized melanin.
Possible reasons for black spots or streaks include:
- Incomplete expression of a melanistic mutation, leading to patchy black areas.
- Accumulation of melanin deposits during feather regrowth after molting.
- Environmental factors like sun exposure or diet influencing melanin levels.
- Injury or damage to a feather follicle resulting in irregular melanin when feathers regrow.
Like fully melanistic individuals, spotted birds are not considered abnormal or unhealthy. The black markings appear randomly and do not indicate sickness or disease.
Conclusion
Black-headed seagulls provide a striking example of natural color variation in common gull species. Rather than a separate species, these dark-plumaged birds represent a naturally occurring melanistic morph that provides diversity to gull populations worldwide. While not as common as normally colored birds, black-headed gulls continue to maintain stable breeding populations and do not appear to be endangered or at risk of disappearing.
So in summary, black-headed seagulls are simply a color variant of regular gull species, rather than any distinct or rare type of bird.
