/* Ensure H1 and H3 headings are visible on mobile */ @media only screen and (max-width: 640px) { h1, h3 { display: block !important; } }
top of page
Search

🪺Nest Box Summary 2024: Insights on Bluebirds, Swallows, and Biodiversity Support

Updated: Jul 17

Published: March 4, 2025 | Contributor: Richard Lombard | Veasey Memorial Park Blog


“We saw 20 tree swallows and 18 eastern bluebirds fledged from our nest boxes…”  

– Richard Lombard, ornithologist & longtime friend of Veasey Memorial Park whose seasonal visits provide invaluable insights into the park’s nesting activity


Each year, Veasey’s fields become a nesting sanctuary for bluebirds, swallows, and a surprising supporting cast of wildlife. Thanks to volunteer scientist Richard Lombard, we have detailed insight into the 2024 nesting season. His report is included in full below -- and spoiler alert: it was a strong year for the birds.


Season Summary

  • Nest Boxes Active: 7 across the Veasey field

  • Species Monitored: Eastern Bluebirds (EABL), Tree Swallows (TRES), House Sparrows (HOSP), Bobolinks (BOBO)

  • Nest Attempts:

    • Bluebirds: 4 nests → 20 eggs → 18 fledglings

    • Swallows: 4 nests → 20 eggs → 20 fledglings

  • House Sparrows: 3 nest attempts disrupted due to predatory behavior (no fledglings)

  • Average Fledglings per Attempt:

    • Bluebirds: 4.5

    • Swallows: 5.0

  • Volunteer Support: Nest boxes built by Georgetown BSA Troop 50 and maintained with help from local scouts

  • Trail & Habitat Improvements: Mowing management supports birds, butterflies, and ground-nesting species

  • Citizen Science Partnership: NestWatch Program, Cornell Lab of Ornithology

🎯 Coming Soon on the Blog  

Stay tuned for a series of highlight posts exploring themes from this year’s nesting season pulled from Mr. Lombard's report:

  • "Bluebird Boom: How Veasey Field Became a Breeding Ground for Native Songbirds"

  • "Swallows & Sparrows: Nest Box Drama in Groveland"

  • "Citizen Science in Action: Scouts & Volunteers Making It Happen"

Sign-up for our newsletter, follow us on Facebook, and never miss an update!

📥 Download Full Report as PDF   Prefer to read the original document with full formatting, graphics, tables, and photos?

Full Report

Nest Box Summary Report – 2024

Submitted by: Richard Lombard Submittal Date: March 4, 2024


OVERVIEW 

There are 7 nest boxes scattered across the field in Veasey Memorial Park (VMP) that provide nesting sites for Eastern Bluebirds (EABL) and Tree Swallows (TRES).  You will notice that 6 of these nest boxes have been placed close together in pairs, and a single nest box at the bottom of the driveway and near the canoe launch.  Though not an obligate cavity nester, the House Sparrow (HOSP) will readily accept a nest box when situated near buildings and other structures.  In past, House Wrens (HOWR) have also used the nest boxes near the woodland edges of the field.   


Unfortunately, house sparrows present challenges by taking nest boxes that would otherwise be available for bluebirds and swallows, which will only nest in natural cavities or nest boxes.  This sparrow is an invasive species and a threat to nesting bluebirds and swallows.  It is not unusual for a male sparrow to enter a nest box, and destroy any eggs and eject nestlings from the box.  If the sparrow encounters an adult, it will often peck the head of its victim resulting in fatal head trauma.  For this reason, any nest attempt by a sparrow is discouraged.   


As our nest boxes have been in the field for several years, it was not surprising that the nest boxes were showing signs of wear and tear, and needed replacement.  Fortunately, six of the boxes were replaced at the beginning of the 2022 nesting season.  The new nest boxes were built by Georgetown BSA Troop 50.  The Troop made the boxes as a team effort, and the Scouts, Nathan Ogden and Bryan Benoit, along with Scoutmaster Dave Lankshear, helped place them in the field.  We are very grateful for their effort and community service, as well as their commitment to Citizen Science.   


NESTING IDENTIFICATION AND BREEDING ACTIVITY 

It is relatively easy to identify what avian species is using a nest box.  The construction of the nest and the size and color of the eggs will make identification a snap.  In the case of a tree swallow, its egg is approximately the same size as bluebird egg but entirely white.  In contrast, a bluebird egg is a robin’s egg blue with no markings.  The egg-size of each species is approximately 0.8 inches in length.  The typical clutch size ranges from 3-5 eggs and 4-6 eggs for the bluebirds and the swallow, respectively.  Both species build similar cup-shaped nests using dry vegetation that is found in the field or nearby woodlands.  The tree swallow characteristically builds a nest with dry grass and lines the nest with white feathers, while the bluebird constructs a nest with pine needles without feathers, thus, differentiating between their nests is easy.  In sharp contrast, a house sparrow builds a rather messy-oversized and whirled-shaped nest made of grasses and almost anything else the adult birds can find, including paper, cigarette butts, cellophane wrappers, and other pieces of trash.  In appearance, a sparrow egg is light in color with brown mottling and similar in size to bluebird and swallow eggs.   


As the house sparrow is an invasive species and a general nuisance and threat to bluebirds and swallows, a concerted effort was made to discourage it from nesting.  To discourage predatory behavior by house sparrows, invasive species management was consistently practiced by removing sparrow nests and eggs.  In many instances when a nest is removed, the female sparrow will attempt another nest in the same box soon after her nest was removed.  There were three nest attempts by sparrows this season.  As this sparrow is a nonnative and invasive species, it is not protected by the Migratory Bird Treaty Act.   


Eastern bluebirds typically will not nest within at least 300 feet of another pair of bluebirds.  On the other hand, tree swallows are more social and less restrictive regarding nesting separation and breeding territory.  Surprisingly, the eastern bluebird and tree swallow show little reluctance to nest next each other.  One reason for this disparity might be that they exploit different foraging stratums.  Bluebirds prefer foraging near or on the ground often swooping from a perch to seize prey, a strategy referred to as “hawking.”  In contrast, swallows are aerial insectivores that forage by gathering prey in flight often well above the ground.  Both avian species feed predominantly on insects and other small invertebrates.  Interestingly, the tree swallow is the only swallow breeding in North America that includes berries in its diet.  Due to their mixed diet, tree swallows return earlier and migrate later from their breeding grounds than any other swallow in North America.  Bluebirds also supplement their diet with berries especially during winter but do not migrate.   


This communal nesting phenomenon can be taken advantage of by pairing nest boxes.  As nesting bluebirds will not nest close to another pair of bluebirds, distances between paired boxes should be separated by at least 300 feet.  With the expense and effort needed to install nest boxes, this arrangement is an efficient nest box configuration.  This practice is exhibited in the Veasey field where six (6) of the seven boxes are arranged in pairs.  The paired boxes are as follows: 12VP/12AVP (near the driveway), 10VP/11VP (near the oak tree) and 16VP/16AVP (at the top of the hill near the woodland edge).  There is single nest box, 1VP, located along the driveway near the canoe launch.   


Due to its larger size, the bluebird has a distinct competitive advantage over the swallow when acquiring a nest box.  As bluebirds typically begin nesting before swallows, a bluebird pair will have selected one of the paired boxes, leaving the other box available for swallows.  The bluebird pair will offer little or no aggression when their neighbor is a pair of swallows, but will fiercely defend their breeding habitat from another pair of bluebirds.  A bluebird pair will often produce a second brood in the same or nearby box.  Being single-brooded, nesting swallows will only use a nest box once during a breeding season.  Swallows are also great sentinels around their nests, and will dive at anything they perceive as a threat.  This behavior also benefits any neighboring nesting bluebirds that they do not consider as threats.   


The bobolink (BOBO) is another species that nest in fields and grasslands, preferring an herbaceous vegetative cover greater than a foot in height.  The bobolink is a little larger than an eastern bluebird.  The male, which is solid-black below and displays large white patches above with a significant olive-colored patch on the nape of its neck, is by far more striking than the female.  The female, which displays buff coloring with extensive striping across the head and back, builds a nest of grasses and other herbaceous vegetation directly on the ground.  Locating a nest is rather difficult as the bobolink immerses or disappears into the vegetation some distance from the nest.  Though, male bobolinks were present in field early in the season, there was no evidence of breeding.  The field has become shrubbier, making it less appealing to bobolinks for nesting.   


The Groveland Highway Department continued to regularly mow and maintain the interconnected Veasey field trails.  These trails provide easier access to the nest boxes, making maintenance and nest monitoring more convenient.  The trails also allow park visitors the opportunity to wander through the field, which is especially pleasant late in the season when vegetation is high.  The trails also afford better viewing of nest boxes and wildlife activity, particularly, butterflies, dragonflies, and other field-loving invertebrates, in addition to the grassland birds.  Delayed mowing has encouraged ground nesting bobolinks and savannah sparrows as well as attracting a bounty of insects and other invertebrates that birds and their young thrive on.  This practice is critical for ground-nesting birds as their young do not fledge until mid-summer.  Since 2005 delayed mowing has been practiced.  For the past several years, goats have been employed to manicure the Veasey field as shown in Photo 2.   


NEST BOX MONITORING 

In the Northeast, bluebirds often attempt their first nest early in April, while tree swallows tend to delay nesting until later in the month or even May, and commonly have finished nesting by July.  Both April and May can present cold and wet weather and limited food opportunities making nesting success challenging.  Though the swallow is single brooded, the eastern bluebird may have 2 or 3 broods during a single season.  In 2024 the estimated first-egg-date (EFED) for the bluebird in the Veasey field was April 18th, while the EFED for the tree swallow was May 7th.  There three (3) house sparrow nest attempts but no nests were allowed to produce fledglings.  Photo 3 shows the first clutch of bluebird eggs of the 2024 season in nest box 12AVP, and Photo 4 presents the hatchlings at about 5 days old.  Photo 6 on the following page, shows the nestlings at about 13 days old.  Bluebirds had 4 nest attempts, producing 20 eggs and 18 fledglings.  Of the 4 nest attempts, 4 successfully produced fledglings.  The average productivity for bluebirds was 4.5 fledglings per nest attempt.   


First Hatchlings of Eastern Bluebirds of the 2024 Season in Nest 12AVP at 5 days - courtesy of Richard Lombard
First Hatchlings of Eastern Bluebirds of the 2024 Season in Nest 12AVP at 5 days - courtesy of Richard Lombard

Tree Swallows made 4 nest attempts, and all were successful, producing a total of 20 eggs and 20 fledglings.  The overall productivity for tree swallows was 5.0 fledglings per nest attempt.   


A Trouble-Shooting Guide for Nest Box Landlords is found in Appendix B.  This guide is helpful for determining the cause of various types of nest predation.  For instance, under the first column of this guide (what you might find) you will notice in the third block down, nestlings found dead in box with signs of trauma.  Moving across to column 2 (3rd block down), you will discover that the possible cause of this event could be due to House Sparrow predation.  In the third column, the guide suggests moving the nest box away from the area inhabited by House Sparrows.   


Table 1 highlights the nest box data for VMP, including the total number of nest attempts and the number of attempts that produced at least one fledgling as well as the total number of eggs, hatchlings, and fledglings.  Since 2008 nest box data has been shared with the NestWatch Program of the Cornell Lab of Ornithology (CLO).  By participating in this program, nest data was available to download as Excel spreadsheets that were most helpful for reviewing and organizing nest box data.  The NestWatch Protocol for Monitoring Nests (Appendix A) was utilized as a monitoring guide. 

 

Table 2 presents additional reproductive data, including, the average number of eggs, nestlings, and fledglings per nest attempt.  During the 2024 nesting season, the average number of eggs per nest attempt for bluebirds and swallows were 4.5 and 5.0 respectively, and within the expected ranges of 3-6 and 4-7 eggs per nest attempt.  The average number of bluebird and tree swallow fledglings per nest attempt was 4.5 and 5.0, respectively.  Overall, tree swallows fared better than bluebirds with a nest productivity of 100%, while bluebird’s nest productivity was 90%.   


Graph 1 on page 7 shows that in 2024 both the eastern bluebird and tree swallow produced an above average number of fledglings compared to the previous years.   


RECOMMENDATIONS 

Nest attempts by House Sparrows in nest boxes must be deterred.  Any sparrow nest with eggs must be removed from the nest box.   

  1. Following each nest attempt, the nest must be removed and from the nest box, and the box must be scraped out to remove any debris.  

  2. Nest box inspection and maintenance prior to the breeding season is necessary to ensure old nest material has been removed and the boxes are clean and as weather-tight as possible.  Caulking cracks and spaces that have developed due to weathering and aging will help minimize weather-related fatalities.   

  

SUMMARY 

Early last century bird watchers noticed that the numbers of their beloved bluebird were diminishing.  Conservationists noted that bluebird habitat was disappearing and the number of natural nest cavities becoming ever scarcer.  The bluebird was also now competing for nest cavities with the house sparrow and European starling that had been introduced from Europe.  Bluebird conservationists like Lawrence Zeleny, implemented conservation measures to reverse this trend.  Throughout the eastern part of the country, concerned conservationists and bluebird enthusiasts began erecting nest boxes specifically designed to attract bluebirds and coincidently Tree Swallows.  A series of strategically placed nest boxes became known as a bluebird trail.   


As revealed in The State of the Birds published by the MAS in 2013, the eastern bluebird has successfully rebounded and is now experiencing an increasing population trend.  The news is somewhat positive for the tree swallow as well.  Unfortunately, the report for many field birds is not so optimistic, such as the American kestrel, bobolink, and several native sparrows.  


During the 2024 season, tree swallows made 4 nest attempts in the Veasey Field producing a total of 20 eggs and 20 fledglings.  In contrast, the bluebirds had 4 nest attempts producing 20 eggs and 18 fledglings.  As the data shows, both species had a high productivity despite all the challenges, especially weather, that can significantly impact nesting success.  Without a doubt, weather will continue to pose a threat with more frequent heat waves, extended droughts, heavy precipitation events and even colder springs that will challenge every nest attempt.  The tree swallow and eastern bluebird both managed to produce an above average year number of fledglings.  Though, male bobolinks were present in field early in the season, there was no evidence of breeding.  One reason for this lack of breeding is that the field has become shrubbier, making it less appealing to bobolinks.   


RESOURCE INFORMATION 

  • Cornell Lab of Ornithology Program.  

NestWatch … http://nestwatch.org/ 


SOME INERESTING NEST BOX FACTS  

Eastern Bluebird:  Sialia sialis - 7 inches in length 

Voice:  Call note – chur-wi or tru-ly     Song – 3 or 4 soft gurgling notes 

Favored Habitat:  Open country with scattered trees, farms, along roadsides. 

Nest: Cavity; either natural tree hole, or bird box. Built by female; a loose cup of grasses, weed stems, pine needles, twigs, occasionally with hair or feathers. Built in 1-6 days. 

Egg laying:  5-7 days (sometimes more) – one egg per day, with at least one day in between eggs. 

Eggs: 3-6, usually 4-5; pale blue, occasionally white, unmarked; 0.8”  

Incubation period: 12-14 days 

Nesting Schedule (after hatching): 

Day 1: Bright coral-pink skin, eyes sealed, down in sparse tufts. 

Day 2 – 4:  Wings, head and spine look bluish due to developing feathers under skin. 

Day 5 –7: Feather sheaths begin to emerge on wings. Eyes still closed. 

Day 8 – 11: Eyes open! Feathers sheathes continue to grow. 

Day 11 – 12: Feathers of wing and tail reveal cobalt blue in males, duller gray-blue in females. Females also show white edging on outer tail feathers. 

Day 13:  CUT OFF DATE FOR BOX CHECKS! Fully feathered young become increasingly active, and may fledge prematurely if box is opened. 

Day 14 – 22: Fledging occurs and first flights. 

Young remain in cover while parents bring food. 

Day 30-on: Fledglings feed on their own. 

 2-3 Broods per season 

 

For comparison: 

 Tree Swallow 

Nest:  Somewhat similar to bluebird but mostly grasses and lined with feathers. 

Eggs:  4-6, pure white without gloss; Incubation:  13-16 days; 1 brood 

 

House Sparrow 

Nest:  Huge ball of grass, weeds, trash with opening on side; very messy; lined with feathers, hair or string. 

Eggs:  3-7, white, greenish white; spotted with grays and browns.  Incubation: 12-13 days; 2-3 broods 

Comments

bottom of page