Monitoring Bluebird Nest Boxes in Pocahontas State Park

Monitoring Bluebird Nest Boxes in Pocahontas State Park

Monitoring Bluebird Nest Boxes in Pocahontas State Park

Why monitor – especially every week?

Increases the chances of success and helps determine population trends.

Check on the progress and health and safety of the birds we have attracted.

Watch for signs of house sparrows and take appropriate action.

Watch for vandalism and/or predation.

Keep detailed records on observations for each box.

Summarize and send data to state and national organizations.

It’s great fun.

How to monitor

Meet in the Logistic Center Maintenance Area.

Retrieve the Notebook and bucket from the tool box and go to the first box.

Read the previous monitor’s comments in the notebook for that box.

Take note of species of adult birds present in the vicinity and any other activity you observe.

Approach the box quietly.

Tap on the outside of the box but do not stand directly in front of the opening in case an adult bird flies out.

Open the box slowly. Don’t open if nestlings are older than 13 days. This may cause them to fledge prematurely. When in doubt about the age of the young, do not open the box.

Note the number of eggs and/or nestlings and estimate the approximate age of nestlings based on visual appearance.

Occasionally the female will stay on the nest when you open the box. Don’t disturb her and carefully close the box. Come back later if you are able or have time.

Close the box, tighten the screw and walk away quickly so the adult can return to the box.

Record your observations on the monitoring form for that box in the field notebook. Add any other comments that might help the next monitor. Be as clear as possible. You can’t write too much - don’t trust your memory.

Fill out the weekly summary sheet, return notebook and bucket to the tool box.

Questions, problems or issues contact trail coordinators - Lee and Jane Hesler (804-768-4201).

Predators, pests and what to do about them

Wasps– scrape out the nest and rub soap on the roof of the box to discourage them.

Snakes– the eggs or young have disappeared. Check to make sure the pole guard is ok. Look for any overhanging branches where a snake might have dropped from. Record the condition and inform the trail coordinator if limbs need to be removed.

Squirrels, raccoons, opossums, cats– the nest will probably be destroyed with eggs and young missing. The Noel guard is designed to limit access by these predators.

Ants– apply petroleum jelly around the pole under the snake guard. If heavily infested inform the trail coordinator who may need to replace the nest.

House sparrows– If dead birds are found in the box with peck marks on the head the cause is most likely house sparrows. These sparrows are non-native and not protected by the USFWS, the Migratory Bird Treaty Act and the Migratory Bird Treaties. We prefer to use passive control which involves removing nests and eggs. Alert the trail coordinator if you suspect house sparrows.

Starlings– Starlings are non-native and not protected. The Noel guard should help protect the bluebird from having eggs or young removed from the nest. Any additional help will need to come from the bluebirds.

House wrens – These native birds will take over a nest box already in use after removing existing eggs or young. Although protected it is possible to take measures to deter their use of a bluebird house. Contact the coordinator if you suspect house wrens are using a box.

Blowflies– The adult fly lays eggs usually under the nest. The larvae suck the blood of the nestlings at night. If possible remove the larvae from under the nest. If a large number are seen ( >50), contact the coordinator who will replace the nest.

Nest building

Nest building takes an average of 4-5 days but can be built in as little as two. In some cases the nest building may be spread over a six week period. The birds may leave and then come back to finish. It is important to note any change in the height of the nest as it is being built.

Inactive nest removal (USFWS by A. Kirk Dec,2006) Nests and/or eggs of any songbird that are inactive in the following situations can be destroyed. The rationale is that when empty, partial or complete nests, or nests with unhatched eggs are left in the box, it blocks new nesting attempts.

1)Partial nests of any songbird that is monitored regularly: Week 1 if there is no more additional nest building in weeks 2,3 or 4, the nest can be removed in the 4th week. Timing restarts when there is any additional nest building.

2)Complete nests of any songbird that is monitored regularly: Week 1 If no eggs are laid in the nest in weeks 2,3 & 4, nest can be removed in the 4th week.

3)Complete clutch of eggs of any songbird that is monitored regularly: If you suspect a nest has been abandoned, touch the eggs. If they are warm they are being incubated. If they are cold they may have been abandoned or are dead. If they are still cold the next week then remove the cold eggs with the nest. A female will usually be back building a new nest within a week or two.

4)House wrens only. Leave partial or incomplete nests in tact the first week you find it. If still no egg cup the 2nd week, destroy the dummy nest. Repeat if necessary. If egg cup or eggs are found in subsequent weeks, allow natural cycle to continue.

Nests of other cavity nesters

Do not remove the nests of other native cavity nesters such as a Carolina chickadee, tufted titmouse, tree swallow, brown-headed nuthatch or house wren. The Federal Migratory Bird Treaty Act of 1918 protects all these birds. We report their nests and numbers to the VBS along with the bluebird data.

The nesting cycle

Bluebirds typically lay 4-5 eggs – one each day in the early morning. The female will begin to incubate when the last or second to last egg has been laid. In this way, the eggs will hatch about the same time. The average incubation time is 12-18 days. In very warm weather incubation may begin early resulting in the hatching occurring over several days.

The hatchlings will grow and be ready to leave the nest after 16-23 days. When the young approach full size, the parents will begin to feed them from the outside of the box. We want to prevent the birds from fledging too early so a box should never be opened after the hatchlings are 13 days old.

When you are sure that the fledglings have left the nest, open the box very carefully and note any unhatched eggs or dead birds. Check under the nest for blowflies or their larvae. If you find them make a note in the log book. Remove the nest and sweep/scrape out the box. Collect the old nest in a bag and dispose of it in a trash bin.

The female always makes a new nest – even on top of the old one. If the nest gets too high in the box it may be easier for predators to reach the nest. The female may start a new nest within a week of the young fledging and start laying eggs immediately. There may be one less egg in the second clutch.

Monitoring equipment list

Bucket or bag to carry everything.

Monitoring log notebook


Disposable gloves

Philips screwdriver

Plastic bags

Brush and scraper

Soap for wasp control

Petroleum jelly for ant control

Alcohol hand sanitizer

Camera and binoculars are optional.

1/12/19 Monitoring Bluebird Nest Boxes LJHesler