Quick Answer
There are a few key reasons why a hummingbird may abandon its nest:
- Predation – Hummingbirds are vulnerable to predators like snakes, cats, and larger birds when nesting. If a predator disturbs the nest, the hummingbird may abandon it.
- Insufficient food sources – Hummingbirds need abundant nectar to raise their chicks. If food sources run out near the nest, they may abandon it.
- Severe weather – Strong winds, heavy rain, or extreme heat could damage the nest or make conditions unsafe for the chicks. This may cause abandonment.
- Infertile eggs – If the eggs laid are infertile, the hummingbird will leave the nest after the typical incubation period.
- Human disturbance – Excessive noise, activity, or touching of the nest by humans could lead hummingbirds to abandon the site.
Predation
Predation is one of the most common reasons why a hummingbird may abandon its nest before the chicks hatch or fledge. Hummingbirds have many natural predators that can threaten their nests including:
- Snakes – Snakes are adept climbers and can raid nests for eggs and chicks. Common predators include rat snakes, garter snakes, and milk snakes.
- Cats – Domestic and feral cats will readily predate on ground and low-hanging hummingbird nests.
- Jays – Birds like blue jays, Steller’s jays, and scrub jays will raid hummingbird nests.
- Crows – Intelligent crows can be significant nest predators.
- Squirrels – Tree squirrels will eat hummingbird eggs and young.
- Chipmunks – While small, chipmunks can still access many hummingbird nests and eat the contents.
If a predator manages to raid the nest and eat the eggs or chicks, the hummingbird parents may have no choice but to abandon the nest site. Even if predators do not directly access the nest, just frequent nearby activity of predators can spook hummingbirds and cause them to leave. Once abandoned, most hummingbirds will not reuse a nest site in the same season if it has been compromised by predators.
Deterrents Against Predators
There are a few tactics that can help deter predators and prevent hummingbird nest abandonment:
– Hang nesting material away from tree trunks which snakes climb. Platform and side-hanging nests are safer.
– Use deterrents around nests like petroleum jelly or hot pepper wax to prevent climbing predators.
– Keep domestic cats indoors or supervised outside during nesting season.
– Use plastic owl or hawk decoys which scare other birds from the area.
– Clip back branches and vegetation around the nest to reduce hiding places.
– Install squirrel baffles on bird feeder poles and nest trees.
– Use predator guards or cages around nests, but ensure they do not overly obstruct the hummingbird’s access or vision.
Insufficient Food Sources
Access to adequate food sources is critical for hummingbirds nesting and raising chicks. Hummingbird chicks need to be fed frequently – as often as every 20 minutes! This means parent hummingbirds need a reliable abundance of nectar-producing flowers near the nest.
If the natural flowering plants and food sources around a hummingbird’s nest decline or disappear, they may be unable to sustain themselves and the chicks. Reasons food sources can be insufficient include:
- Hot, dry weather causes flowers to wilt and die off.
- Heavy rain washes away nectar from flowers
- Lack of rain leads to poor flowering
- Areas near feeders are picked clean and not replenished
- Competing hummingbirds deplete food supplies
- Butterflies, bees, and other pollinators reduce availability
If faced with dwindling food, hummingbird parents must make the tough choice between their own survival and the chicks. In most cases, the adult birds will abandon the nest to seek out new nectar sources.
Providing Adequate Food
To help prevent nest abandonment due to insufficient food:
– Maintain multiple nectar feeders near nesting sites and keep them freshly filled.
– Plant diverse, hummingbird-favorite flowers and change plantings for continuous blooms. Favorites include bee balm, coral honeysuckle, trumpet vine, and cardinal flower.
– Improve water sources like bird baths and trickling fountains, so hummingbirds can easily drink and bathe.
– Consider using feeder guards to deter other species from stealing nectar.
– Avoid pruning flowers or trees near hummingbird nests during nesting season.
– If extreme weather occurs, provide alternative food sources like sugar water if flowers decline.
Severe Weather
Sudden storms, extreme winds, heavy rain, hail, and temperature swings can all negatively impact hummingbird nests. Nests are naturally exposed and vulnerable to weather shifts. Extreme conditions that might cause abandonment include:
- Strong winds blowing nests out of trees or knocking them to the ground
- Driving rain flooding or soaking nests
- Hail pelting and breaking eggs
- Early hot spells overheating chicks and reducing insect food
- April snowstorms chilling eggs and nestlings
- Dry heat and drought shriveling food sources
Nesting hummingbirds seem to be sensitive to quick changes in barometric pressure and storm fronts. Some research indicates hummingbirds can sense dropping pressure and will abandon nests prior to severe weather arriving.
Even if the nest stays intact through a storm, the parents may abandon a site if they feel it is no longer safe or viable after weather damage. They will then find a new nesting area in better protected shelter.
Protecting Nests from Weather
To help hummingbird nests endure weather shifts:
– Provide sturdy, sheltered nesting areas on porches, under eaves, or within tree canopies.
– Avoid excessively exposed nest spots like lone branches or wires.
– Relocate vulnerable nests to more protected areas before storms.
– Gently secure loose nests with breathable mesh or material if needed.
– Add temporary nest coverings if hail or wind is expected, but avoid fully enclosing the nest.
– Maintain normal temperatures and moderate airflow around nests during heat waves or cold snaps.
– Ensure nearby feeders and food sources are available after damaging weather.
– Improve drainage around nests so they dry out faster after heavy rains.
Infertile Eggs
If a hummingbird nest contains infertile eggs that will never hatch, abandonment is inevitable. Hummingbirds incubate their tiny eggs for about 2 weeks before expecting hatchlings.
If chicks do not emerge after the typical incubation period, the parent birds will leave the nest permanently. Common causes of infertile hummingbird eggs include:
- Poor mate selection – Young, inexperienced, or incompatible mates may fail to adequately mate.
- Stress – Nest disturbances, lack of food, or inclement weather can affect egg viability.
- Old age – Older females lay fewer quality eggs due to reproductive decline.
- Genetic issues – Inbreeding in isolated populations increases infertility risks.
- Abnormal temperatures – Exposure to extreme heat or cold during egg formation.
- Environmental toxins – Pesticides, chemicals, pollution, and radiation can interfere with embryo development.
Hummingbirds produce only 2 tiny eggs per clutch, so infertility severely limits reproductive success. If nest abandonment occurs due to infertile eggs, hummingbirds will often build a new nest and lay a new egg clutch elsewhere.
Improving Fertility
Steps that may boost hummingbird egg fertility include:
– Providing optimal springtime temperatures and protection from extremes.
– Reducing pesticide usage and exposure to air pollution near nest sites.
– Limiting disturbance and stressors around nesting areas.
– Ensuring female health through adequate food and minerals.
– Allowing optimal mate selection and competition rather than isolated breeding.
– Installing nest perches which facilitate mating.
– Supplementing minerals through a salt lick or nectar mix.
Human Disturbance
Excessive noise, activity, touching, and other human interference near hummingbird nests often causes nest abandonment. Hummingbirds seem especially sensitive to human disturbance compared to other species. Some common nest disturbances that lead hummingbirds to abandon nests include:
- Loud music, machines, barking dogs, or other noises near the nest
- Frequent pedestrian traffic and activity under or near nests
- Children playing, shouting, or tapping on nest trees
- Pruning or manipulating nest trees and branches
- Touching or rattling the nest
- Getting too close to take photos
- Leaving abandoned ladders, tools, or debris by nests
- Installing fake owls or deterrents too close after nest building
Excess activity stresses hummingbirds and makes them feel insecure about their nest site. If they sense the area is frequently disturbed and potentially unsafe, they will abandon the site for a more secure location. This most often occurs during the nest building stage, but disturbance can cause abandonment anytime.
Limiting Disturbance
To avoid forcing hummingbirds to abandon nests:
– Mark or fence off nest areas to avoid unintentional disturbance.
– Post signs alerting people to avoid the vicinity and why.
– Route walking paths and work sites away from active nesting areas.
– Keep noise to a minimum near nesting zones.
– Limit the use of deterrents, ladders, and machinery after nest building begins.
– Prevent unrestrained pets from agitating nesting hummingbirds.
– Refrain from excessive nest photography and monitoring. Watch activity from a distance.
– Build protected nesting shelves or sites away from human activity.
– Wait to prune trees and vegetation until hummingbird young have successfully fledged.
When is Abandonment Normal?
In some cases, nest abandonment by hummingbirds is expected and part of their natural breeding biology rather than the result of external problems:
- Nest relocation – Hummingbirds may abandon a first nest to build a new one in a better site before eggs are laid.
- After fledging – Once the young can fly and feed themselves, parents leave the empty nest for good.
- Second nests – Males take over the first nest duties so females can build a second nest elsewhere.
- Nomadic breeding – Some tropical species naturally exhibit loose nest bonds and frequent relocations.
As long as the parents are still feeding and attending to young in the nest, abrupt abandonment generally signals an underlying issue that should be addressed in the future through improved nest sites, predator deterrents, reducing disturbances, and providing adequate food resources.
Conclusion
Hummingbird nest abandonment often occurs as a result of predation, lack of food, severe weather, infertile eggs, or human disturbance. While some temporary abandonment can be normal, permanently deserted nests usually indicate a problem with the nest site or environment. This prevents hummingbird chicks from successfully hatching and fledging.
To reduce unnecessary nest abandonment, homeowners and bird enthusiasts can take various steps to protect and improve the nesting conditions. This includes deterring predators, supplying steady food sources, minimizing activity near nests, providing sturdier nesting locations, and limiting use of pesticides and pollutants.
With proper hummingbird-friendly habitats, the adult birds can feel secure continuing to incubate eggs and raise young through to fledging rather than abandoning their nesting efforts. Careful support of hummingbird reproduction ensures future generations of these unique, delicate birds.
