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Providing For Bluebirds: Guidance for Bluebird Nest Box Establishment in South Carolina

Why Bluebirds

Bluebird populations in North America have been in decline due in part to the loss of habitat. Bluebirds are secondary cavity nesters. They do not drill their hole for a nest but use an abandoned hole that was made by another bird, such as a woodpecker. As forested and agricultural land is converted to urban and suburban areas, dead trees which are critical to cavity nesters, are removed reducing the supply available for nest construction. In addition to habitat loss, the introduction of two non-native birds, the European Starling and the House Sparrow, have also contributed to the decline of Bluebirds. Both species are cavity nesters and will compete with Bluebirds aggressively and can even predate Bluebird eggs and young. Currently, Eastern Bluebird populations have stabilized, due in part to conservation efforts of community members who provide Bluebird nesting boxes, commonly referred to as birdhouses. This fact sheet is focused on the establishment of a community Bluebird trail but can also provide guidance to someone wishing to install one or two Bluebird nest boxes.

Habitat/Life Cycle

Bluebirds are insectivores, approximately 2/3rds of the diet of an adult Bluebird is made up of insects and other invertebrates including grasshoppers, beetles, spiders, earthworms, crickets, snails, etc. The remainder of the Bluebird diet is wild fruits including wild grapes, dogwood, sumac, blackberries, bayberries, etc. Bluebirds prefer habitats that are open such as farms, golf courses, greenways, and schoolyards, but can also do well in suburban areas where space is available.

There are three species of Bluebirds in North America, the Eastern, Western, and Mountain Bluebirds. South Carolina is home to the Eastern Bluebird, a resident bird that will remain year-round. In this factsheet “Bluebird” is referring to the Eastern Bluebird in South Carolina with applications more broadly. In South Carolina, the Bluebirds will begin to identify a nesting location in winter as early as December. Bluebirds lay one egg every day for up to 5 to 6 days. Incubation begins after the last egg is laid. Typically the eggs will incubate for 2 weeks (12-14 days), then the chicks will remain in the nest for another two to three weeks before fledging. Bluebirds can have up to three broods a year. Ideally, Bluebird boxes are erected in February but can be placed at any time of the year due to the multiple broods. It may take Bluebirds a few years to locate a Bluebird box; even if it doesn’t succeed in year one, this is no reason to give up. Other native cavity nesters will utilize Bluebird boxes and include the Carolina Wren, Tufted Titmouse, and Chickadee. Use of the boxes by these native species should be welcomed.

Bluebirds will typically lay up to six eggs in a brood. In South Carolina, Bluebirds may have up to three broods in a nesting season which typically runs February through September.

Bluebirds will typically lay up to six eggs in a brood. In South Carolina, Bluebirds may have up to three broods in a nesting season which typically runs February through September.
Kim Morganello, ©2023, Clemson Extension

Bluebird eggs will typically incubate for 12 to 14 days. The chicks will remain in the nest for another two to three weeks before fledging.

Bluebird eggs will typically incubate for 12 to 14 days. The chicks will remain in the nest for another two to three weeks before fledging.
Kim Morganello, ©2023, Clemson Extension

Bluebird Box

Bluebird box also called a nesting box or more commonly a birdhouse, can be built or purchased. This factsheet does not provide specific construction instructions but does include specific features to include regardless of purchasing or constructing your own.

Due to the predation previously mentioned, the entry hole of a Bluebird nesting box should not be more than 1.5” in diameter. This will prevent entry of many predators including the European Starling.

Bluebird boxes are ideally mounted on a pole as bluebird parents like to stand on top of the box to survey the area and look in all directions. Mounting on a pole also helps to deter intruders, a smooth round pole works best such as an electrical conduit. If Bluebird boxes are mounted on a pole, it is strongly encouraged that a baffle or other form of deterrent is included. A baffle or predator guard will deter climbing intruders, including snakes.

Do not use a Bluebird box that has a perch outside of the entry hole, this perch will only encourage invasion from species such as the Crows and BlueJays. A predator will perch on the stand and reach into the nesting box.

All Bluebird boxes should have a side or top that opens to allow for routine maintenance and monitoring. During nesting season, Bluebird boxes should be monitored at least one time a week. Bluebird boxes should be placed at least 5 feet in height but can be as high as 20 feet. Of course, the higher the box is placed, the more complicated monitoring becomes. However, boxes placed too low, such as below eye level, will be more susceptible to predators.

Mounting the Bluebird nest box on a pole with a baffle or predator guard will help to deter intruders that could harm the eggs and baby chicks.

Mounting the Bluebird nest box on a pole with a baffle or predator guard will help to deter intruders that could harm the eggs and baby chicks.
Kim Morganello, ©2023, Clemson Extension

John Piret, a Master Gardener and Bluebird trail monitoring volunteer, installs a numbered Bluebird box labeled “7.” Each box on a Bluebird Trail should have a number to help record data.

John Piret, a Master Gardener and Bluebird trail monitoring volunteer, installs a numbered Bluebird box labeled “7.” Each box on a Bluebird Trail should have a number to help record data.
Kim Morganello, ©2023, Clemson Extension

Bluebird Trail

A Bluebird trail is simply a series of Bluebird boxes that not only provides an opportunity to create nesting habitat for local Bluebirds, but also offers a chance to monitor the local population. Bluebird trails can be as long or as short as desired and space is available. If a subdivision, golf course, school, park, or land owner would like to establish a Bluebird trail, it is important to consider who will do the monitoring & how to recruit, train, & retain the volunteer monitors. To increase the likelihood of success for your Bluebird trail, follow these best practices:

Nestbox Placement

  • Nestboxes should be 100 yards apart to start, over time adjustments might be able to be made to place the boxes closer to each other.
  • Face nestbox away from prevailing winds.
  • Ideally, find a location with a tree, shrub, or fence approximately 100 feet from the nestbox; this will provide a safe place for fledglings to land when learning to fly.
  • Place nestbox at least 50 feet away from heavily wooded areas to avoid competition from House Wrens.
  • If possible, have a nestbox in place in February as Bluebirds begin to scout for nesting sites.
  • A nestbox can stay up year-round to provide shelter.
  • Remove debris from boxes that stay up year-round to prepare for nesting season.

Monitoring Best Practices

  • Monitor the trail at least one time per week from February to September.
  • Volunteers should use a data sheet to record activity; an example of a data-sheet is included at the bottom of this factsheet. Recorded data includes date, observer, time, brood number, the species nesting, number of eggs, number of young, number of fledged, and any comments.
  • To know what to look for, bring data sheet from the previous monitoring session. Keep data sheets in a binder or other organization tool, which could be an electronic device.
  • Bluebirds are not scared by humans, in fact, they are highly tolerant. However, it is still best to keep voices down and avoid unnecessary disturbance; also keep visits brief.
  • Monitoring the boxes will also encourage management of pests such as wasps, fire ants, or mice. Irish Spring bar of soap can be used to spread on the underside or inside of a box and along the roof to deter wasps.
  • Avoid monitoring during harsh weather or extremely cold conditions; the mom may need to stay on the eggs to keep temperatures moderated.
  • Monitor in the morning but not at first light. The female may be laying eggs or sitting on eggs while temperatures are still low at dawn.
  • Knock first before opening the top or side of the box, this will notify any birds to present that they have a visitor. Adults may fly out but will return.
  • For safety purposes always monitor with a friend or assure someone knows where you are.
  • Always wear gloves while cleaning out the nestbox and wash hands afterwards. Do not allow the debris to be inhaled or get into the eyes.
  • Since the boxes are elevated, a step stool or small ladder may be needed to view the box from the top. One person should stable the ladder or step stool, while the other person climbs up to observe the nesting activity.
  • Once chicks are in the nest, it is best to observe using a top panel, as opposed to the side panels since a chick may easily tumble out.
  • After the eggs have hatched, and the chicks are greater than 10 days old, observe from a distance to avoid spooking the chicks and causing them to fledge early.
  • After the birds fledge, remove all nesting material and let the Bluebird parents start over. Bluebirds will build on top of existing nest material, but this can lead to parasites and can attract fire ants and other pests.
  • Use your best judgment, if eggs have not hatched 3 to 4 weeks after being laid, they are not viable and should be removed. Also, remove any cracked eggs or deceased young. Old nesting material, non-viable eggs, cracked eggs, or deceased birds that are removed should be disposed of in a location away from the nesting box; this material can attract predators if placed too close to the box.
  • If the nestbox is used by another native bird such as a Chickadee, Titmice, Nuthatch, etc, note the type of nesting material utilized in the box. The type of material will help to determine which species of bird is using your nesting box. Do not destroy these nesting efforts, yet record as you would the Bluebird.
  • Data recorded can be provided every year to Cornell Laboratory of Ornithology.

What to bring when monitoring:

• A friend.

• Irish Spring bar of soap which can be used to deter wasps, spread the soap on the underside or inside of the box if wasps are an issue.

• Gloves to remove nests once chicks have fledged (left the nest) and hand sanitizer.

• Paper bags to place removed nest material.

• Hand mirror which can be used to hold over the box, open a top panel and hold the mirror in a way that allows you to view the nest. This can be helpful with active chicks.

• Step stool or small ladder.

• Wire brush and paintbrush to use when removing debris both inside or outside of the nesting box.

• Data sheets to record activity. This information can be placed in a centralized location so that others monitoring the trail can access the data before monitoring. This is helpful to have an idea of what to look for; for example, if the eggs were laid two weeks ago, keep an eye out for chicks!

Karen Piret, a Master Gardener and Bluebird trail monitoring volunteer, approaches a Bluebird box from the side . To avoid startling any birds that may be inside the box, she gently knocks on the side to alert them of her presence.

Karen Piret, a Master Gardener and Bluebird trail monitoring volunteer, approaches a Bluebird box from the side . To avoid startling any birds that may be inside the box, she gently knocks on the side to alert them of her presence.
Kim Morganello, ©2023, Clemson Extension

Caroline Counts, a Master Gardener and Bluebird trail monitoring volunteer, writes down information on the data sheet as others check the boxes. A designated recording space is important to assure data stays organized and accurate.

Caroline Counts, a Master Gardener and Bluebird trail monitoring volunteer, writes down information on the data sheet as others check the boxes. A designated recording space is important to assure data stays organized and accurate.
Kim Morganello, ©2023, Clemson Extension

Case Study

In 2018, a twelve-box Bluebird trail was established at the Clemson University Coastal Research and Education Center located in Charleston, SC. This property is suitable habitat as it includes farmland, native perennials, fruit trees, shrub thickets, and a water source. Clemson University and Clemson University Cooperative Extension staff supported the effort by assisting with trail design, procurement of materials, and installation. The Tri-County Master Gardeners Association performs routine monitoring of the trail one to two times weekly from February to September of each year. Data was recorded and in five years, 161 Bluebird chicks fledged.

Table 1: CU CREC Bluebird Trail Annual Summaries, Charleston SC

Year #Eggs #Lives Young #Fledged #of Boxes
2018 45 30 30 12
2019 57 41 40 12
2020 41 23 22 6
2021 42 37 37 6
2022 46 32 32 11

One of the interesting aspects of establishing a trail is noting what areas are most successful and which areas are least productive. Through the diligent monitoring of the Master Gardeners, trends were able to be observed on which area of the farm is preferred habitat for the Bluebirds. See the following graphics, each line in a ring represents one Bluebird that fledged.

2018

In 2018, there were 12 Bluebird boxes that produced 45 eggs, 30 live young and 30 fledged. All were Bluebird species. The percentage of boxes used was 50% and the percent of eggs that fledged were 67%.

In 2018, there were 12 Bluebird boxes that produced 45 eggs, 30 live young and 30 fledged. All were Bluebird species. The percentage of boxes used was 50% and the percent of eggs that fledged were 67%.
Kim Morganello, ©2023, Clemson Extension

2019

In 2019, there were 12 Bluebird boxes that produced 57 eggs, 41 live young and 40 fledged. All were Bluebird species. The percentage of boxes used was 58% and the percent of eggs that fledged were 70%.

In 2019, there were 12 Bluebird boxes that produced 57 eggs, 41 live young and 40 fledged. All were Bluebird species. The percentage of boxes used was 58% and the percent of eggs that fledged were 70%.
Kim Morganello, ©2023, Clemson Extension

2020

In 2020, there were 6 to 12 Bluebird boxes. Due to COVID restrictions, there are significant data gaps in 2020. Observed were 41 eggs, 23 live young, and 22 that fledged. All were Bluebirds. The percentage of boxes used was 50% and the percent of eggs that fledged were 53%.

In 2020, there were 6 to 12 Bluebird boxes. Due to COVID restrictions, there are significant data gaps in 2020. Observed were 41 eggs, 23 live young, and 22 that fledged. All were Bluebirds. The percentage of boxes used was 50% and the percent of eggs that fledged were 53%.
Kim Morganello, ©2023, Clemson Extension

2021

In 2021, there were 6 Bluebird boxes. Due to COVID restrictions, the number of Bluebird houses were reduced for monitoring purposes. Observed were 42 eggs, 37 live young, and 37 that fledged. All were Bluebirds. The percentage of boxes used was 66% and the percent of eggs that fledged were 88%.

In 2021, there were 6 Bluebird boxes. Due to COVID restrictions, the number of Bluebird houses were reduced for monitoring purposes. Observed were 42 eggs, 37 live young, and 37 that fledged. All were Bluebirds. The percentage of boxes used was 66% and the percent of eggs that fledged were 88%.
Kim Morganello, ©2023, Clemson Extension

2022

In 2022, there were 11 Bluebird boxes that produced 46 eggs, 32 live young, and 32 that fledged. All were Bluebird species except one. The percentage of boxes used was 63 % and the percent of eggs that fledged were 69%.

In 2022, there were 11 Bluebird boxes that produced 46 eggs, 32 live young, and 32 that fledged. All were Bluebird species except one. The percentage of boxes used was 63 % and the percent of eggs that fledged were 69%.

2018-2022

The 2018-2022 activity, suggests that the Bluebirds prefer habitat at the farm that is open but includes nearby mature trees. Boxes placed in open fields were the least productive. Preferences may vary by location. The results of this case study can help to inform the future of the Bluebird trail at this site, as well as provide insight into trails at other locations.

The 2018-2022 activity, suggests that the Bluebirds prefer habitat at the farm that is open but includes nearby mature trees. Boxes placed in open fields were the least productive. Preferences may vary by location. The results of this case study can help to inform the future of the Bluebird trail at this site, as well as provide insight into trails at other locations.
Kim Morganello, ©2023, Clemson Extension

 

 

 

 

 

 

 

 

 

 

 

Nest Box Monitoring Form

Nest Box Monitoring Form

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

For more information:

  • Visit Audubon South Carolina https://sc.audubon.org
  • North American Bluebird Society https://www.nabluebirdsociety.org
  • South Carolina Bluebird Society https://southcarolinabluebirds.org
  • The Cornell Lab of Ornithology https://www.birds.cornell.edu/home/
  • Wild Birds Unlimited https://www.wbu.com

References:

  1. Potter, E.F. et al. (2011) Birds of the Carolinas. Chapel Hill, North: The University of North Carolina Press.
  2. NABS Factsheet: Monitorird nestboxes
  3. Berger, C., Kridler, K. and Griggs, J.L. (2001) The Bluebird Monitor’s Guide. New York: HarperResource.
  4. NABS Fact Sheet Monitoring Bluebird Nestboxes (May 2012) North American Bluebird Society. Available at: http://www.nabluebirdsociety.org/PDF/NABSFactsheetMonitoring.pdf/ (Accessed: March 27, 2023).
  5. NABS Fact Sheet Frequently Asked Questions (May 2012) North American Bluebird Society. Available at: https://www.nabluebirdsociety.org/PDF/NABSFactsheetFAQs.pdf/ (Accessed: March 27, 2023).
  6. Personal Interview: Morganello, K.C. and Fifer, C. (2018) “Bluebird Trail Establishment at the Clemson Coastal Research and Education Center.”
  7. Personal Interview: Morganello, K.C. and Counts, C.S. (2023) “Bluebird Trail Monitoring: Lessons Learned at the Clemson Coastal Research and Education Center.”
  8. Personal Interview: Morganello, K.C. and Tyrell, J. (2022) “Bluebird Trail Monitoring Best Practices From Pilot Efforts in South Carolina.”

Originally published 4/23

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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