Bird eating spiders are large, hairy spiders that have developed a reputation for preying on birds. Their common names like “bird eating spider” or “bird catcher spider” make it sound like birds are a regular part of their diet. But do these giant arachnids really eat birds, or is that just hype?
Do bird eating spiders hunt and eat birds?
There are over 40 species of tarantulas that are informally referred to as “bird eating spiders.” The largest and most notorious is the Goliath birdeater spider of South America. True to its name, the Goliath birdeater does occasionally eat birds. These massive spiders have up to a 12 inch legspan, making them the largest spider species in the world. With their size and speed, they are capable of capturing and feeding on small birds, mice, lizards, and frogs.
That said, a bird eating spider’s diet consists mainly of insects and other invertebrates such as earthworms. Vertebrate prey like birds, mice, and lizards are an irregular supplement to their diet when the opportunity arises, rather than a regular food source.
There are also other large tarantula species from around the world that are known to eat birds on occasion, such as:
- Brazilian salmon pink birdeater
- Colombian giant redleg tarantula
- Usambara orange baboon spider
- Asian forest scorpion
Like the Goliath birdeater, these spiders are certainly capable of overpowering and eating small birds, but insects and other small prey make up the mainstay of their diets.
How do bird eating spiders catch birds?
Giant spiders employ a combination of stealth, speed, venom, and strength to capture bird prey. Here is an overview of bird hunting tactics used by large tarantula species like the Goliath birdeater:
- Stealth – Tarantulas rely on camouflage and patience to ambush prey. They often wait perfectly still for long periods until prey wanders close.
- Speed – When prey gets in striking range, tarantulas can move extremely quickly to pounce and subdue with their legs.
- Venom – Potent venom quickly immobilizes prey and starts digesting the body from within.
- Strength – Their large size and muscle power allows tarantulas to overpower rodents, lizards, frogs and small birds.
In terms of hunting birds specifically, the giant spider will patiently wait camouflaged on the forest floor or against a tree trunk. When a small bird like a hummingbird or finch lands nearby, the spider strikes before the bird can react. The spider’s speed and venom allow it to immediately subdue even agile avian prey.
How do bird eating spiders kill and eat birds?
Once a bird eating spider has captured bird prey, it kills the bird through envenomation. The spider will first deliver a fast-acting venom to rapidly paralyze and partially digest the bird. The spider may also use its pedipalps – small leg-like mouth parts – to help subdue the prey.
After the bird dies, the spider begins liquifying its internal organs and tissues with digestive enzymes. Over a period of 1-2 weeks, the spider will slowly drink the liquefied nutrients of its prey. Only feathers, beaks, talons, and other inedible parts are left behind.
These giant spiders have expandable stomachs that can increase in size substantially to accommodate huge meals. This allows them to ingest prey even larger than themselves. A single large bird can provide sustenance for weeks or months before the spider needs to hunt again.
Do bird eating spiders regularly prey on birds?
While certainly capable of catching and eating birds, spiders do not regularly feed on avian prey. Small birds, mice, lizards and frogs are more like supplemental bonuses to their normal insectivorous diet. This gives rise to the question – why aren’t birds a bigger part of their menu?
There are a few key reasons why spiders do not regularly hunt birds:
- Birds can more readily detect and escape spiders than insects can.
- The energy required to catch birds is high, whereas insects are easy prey.
- Their infrequent feeding habits mean they do not need to extensively hunt vertebrates.
In short, catching insects provides plenty of nutrition without the difficulty and energy expenditure of subduing dangerous prey like birds. Think of vertebrate prey as an occasional treat for these spiders, not a dietary staple.
What species of birds do bird eating spiders prey on?
Goliath birdeaters and other large tarantula species feed on a variety of small bird species, especially:
- Hummingbirds
- Finches
- Sparrows
- Warblers
- Chickadees
Larger threatened birds they may prey on include:
- Macaws
- Toucans
- Troupials
- Wood quail
In terms of weight, spiders can take down birds up to around 150 grams, which is just under 1/3 pound. Larger birds like parrots and raptors have nothing to fear from these spiders!
Are bird eating spiders a significant threat to wild bird populations?
The occasional predation of small birds by spiders is not considered a major threat to overall bird numbers. While startling, such predation events are rare and transient.
Bird populations face far greater threats from issues like:
- Habitat destruction
- Human activity
- House cats
- Pesticides
- Climate change
- Invasive species
Next to these persistent, widespread dangers, the sporadic loss of a few birds to giant spiders has little overall population impact. Additionally, birds have evolved defenses and vigilance to detect stealthy spiders before they strike.
In areas where large tarantulas are native, the local birds have coexisted with them for millennia. While they must be wary of spiders, bird populations remain healthy despite this predation pressure.
Are bird eating spiders dangerous to humans?
Giant “bird eating spiders” rarely bite humans, and actively avoid contact with people. While they certainly look menacing, species like the Goliath birdeater are not considered medically dangerous:
- Their venom has a low toxicity that is milder than a bee or wasp sting.
- They have relatively mild dispositions and are not aggressive.
- Their fangs cannot easily penetrate human skin.
That said, their large size means a defensive bite could cause mechanical injury. But there are no confirmed records of significant envenomation or fatalities.
Basic precautions like leaving them alone, not touching them bare-handed, and not intentionally threatening or provoking them will ensure human safety around these gentle giants.
Conclusion
While capable of killing and eating small birds, giant “bird eating spiders” do not regularly feed on avian prey. They are opportunistic predators that will eat a bird on occasion, but the bulk of their diet consists of insects and invertebrates. Their appetite for birds is limited by the energy required to catch them and the abundance of easier insect prey.
Bird populations face far greater threats from human activity and environmental issues than from occasional spider predation. And these spiders pose minimal danger to humans when left alone. While the moniker “bird eating spider” may be exaggerated, it refers to a remarkable capability of these enormous arachnids.
