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Why Are Bluebirds Eggs Gone?

Why Are Bluebirds Eggs Gone?

It is essential to monitor your bluebird nest box at least once or twice a week. Since bluebirds are tolerant of humans, they are unlikely to abandon a properly monitored nest box. I recommend that you build your bluebird box so that you can open it from either side as well as top and bottom. An unmonitored bluebird nest box may pose more threats to the birds. Moreover, monitoring increases the likelihood of bluebirds nesting in your box and lets you know whenever the bluebirds encounter challenges with competitors and predators.

If the eggs have disappeared, but the nest box seems undisturbed, possible culprits include raccoons, sparrows, wrens, or snakes. However, if you find the eggs shattered on the ground, it could result from an invasion by a red squirrel or chipmunks.

When monitoring a box, you could quickly determine the types of species nesting, thereby examining the eggs and nesting materials. To keep track of bluebird eggs, ensure to record the date and number of eggs you observe. As a result, this will help you know when the eggs are likely to hatch or whether they are fertile or not. 

Like most cavity nesters, female bluebirds lay one egg each day until they complete the entire clutch. Also, bluebirds have an incubation period of about twelve to fourteen days, depending on the temperature of the breeding zone. Read on to find out why the bluebird eggs in your nest box have gone missing and how to prevent such future occurrences.

Why Are Bluebird Eggs Missing?

After you finish building a bluebird nesting trail, don’t expect all of the nests to have bluebirds. In addition to intruders, predators pay frequent visits to bluebird nests, which discourages bluebirds from brooding in the spot. Fortunately, below are some tips I have prepared which could help you with such challenges.

Finding little sticks in your nest box, sometimes even on an already existing nest, is a solid sign enough to alert you of intruding wrens trying to nest in the bluebird nesting box. If the eggs are missing and instead of grass, you find debris, including weeds and paper, proof that sparrows have invaded the bluebird nest. If you find the eggs missing, but the parents are still hanging around, possible culprits could be a cat, snake, or a sparrow. 

On the other hand, if you notice any missing eggs since your last count, inspect the remaining ones to understand who the culprit is. If you can see minute, almost invisible eggs pecked in the eggs, the most likely intruder ought to be a wren. But if the nest has been partially pulled out of the nest box and the eggs are gone, a cat or raccoon might have gained access to the bluebird house.

To know whether mice have intruded and perhaps made a nest in your bluebird nest box, check for seeds, coneflower seed heads, and milkweed in the nesting box. Similarly, there are reported instances where instead of the typical small bluebird eggs, you find blue but larger ones similar to a robin’s eggs. In this case, it is more likely that starlings have invaded your bluebird box and even made a nest.

Other bluebird predators that can damage the eggs are house wrens, Woodpeckers, and house sparrows. Similarly, predators such as fire ants attack and kill recently hatched eggs and young bluebirds. Other predators that typically eat bluebird eggs, adult bluebirds, and young birds include raccoons, cats, and snakes.

Also, remember that since sparrows and starlings are invasive birds, you could take them out of the nest if you like without any legal concerns. However, other birds such as nuthatch and chickadee are songbirds; thus, you should allow them to hatch and raise their brood in your nest box.

European Starlings and House Sparrows, also referred to as English Sparrows, are non-native bird species originating from Europe. These species are infamously known for their aggressive seizure of cavity nest sites meant for bluebirds. As a result, this makes them the primary reason for the tremendous decline of the bluebird population in most states. 

Also, house sparrows have a smaller size allows them to enter most bluebird nests readily. More often than not, they kill nestling and adult bluebirds, destroy their eggs, and chase them out of the nest boxes. As a result, you should at no point allow them to nest or brood in bluebird nesting boxes. Allowing them to nest will increase House Sparrows’ population, further reducing the number of bluebirds. 

Furthermore, a suitable and seamless way of preventing this occurrence is to build your bluebird house correctly or purchase correctly built nest boxes. To ascertain that yours meets the minimum requirements and matches the latest bluebird box standards, check to ensure that it has enough ventilation holes, a predator guard, and drainage holes. For example, you could incorporate the predator guard on the mounting pole, in the spot, or both locations. Also, ensure that you properly size the holes based on the size of bluebirds in your area and clean out the nest after the end of every brooding season.

How Many Eggs Does A Bluebird Lay?

A female bluebird typically lays up to four or five eggs. However, there are reported cases where a single bluebird lays up to seven eggs. During the whole season, the bird lays a single egg each day. Also, there are rare occasions where two females decide to lay eggs in the same nest and take turns incubating and feeding the chicks. 

More typically, however, a female bluebird will not entertain other bluebirds in her nest. As such, they fight any intruding females who want to share the nesting box.

Why Will Some Eggs Fail To Hatch?

Some of the more probable reasons why a bluebird egg may fail to hatch include extreme temperatures. Cold weather especially is a significant problem for bluebird eggs and nestlings. Similarly, exposure to pesticides, bacterial infection, and genetic malformation are also probable causes of unhatched bluebird eggs.

With bluebirds being an interesting species, many bird enthusiasts develop an interest in their well-being from the moment the egg hatches up to when they can fly and fend for themselves. However, increased predators and intruders such as sparrows and raccoons have resulted in the dramatic decline of these birds. With the above information, you now understand why your eggs are missing from their nest and prevent such future occurrences.