Quick Tips: During nesting season, quickly, quietly and carefully check on nestboxes once or twice a week in the afternoon so you can identify and address any problems. Avoid monitoring in early morning, dusk, or during wet cold weather, or when young are close to fledging. A little carelessness can result in accidental destruction or parents deserting a nest.
You've set up or inherited a bluebird nestbox, or maybe even a trail of houses. Let's start by assuming that your goal is to encourage successful reproduction by bluebirds, Tree Swallows and other native birds that nest in cavities. If you want that to happen, you can't just put up boxes and forget about them. For example, in the fall I erected 12 boxes at a closed landfill. The first time I checked them in the spring, nine were filled with hundreds of paper wasps, and never would have been used, even though there were a number of bluebirds and Tree Swallows in the area.
In the past, these birds nested in holes created by nature or other creatures like woodpeckers. However, once people introduced aggressive House Sparrows and starlings that evict or kill birds using cavities, allowed cats to roam, and exchanged open space for development, it became much more difficult for these native birds to survive and breed. They now rely heavily on nestboxes provided by humans.
Bad things can happen in boxes that are not monitored. For example, wood can rot or separate, allowing chilling rain to wet nestlings. House Sparrows may attack and destroy eggs, nestlings and incubating adults. House Wrens may fill up boxes with dummy nests, making them unavailable. Squirrels may chew and enlarge entrance holes that then allow starlings and other predators access to eggs or babies. Paper wasps or fire ants can invade boxes, preventing nesting altogether, driving parents away, or killing babies. Honeybees may use nests.Blowfly larvae can suck babies blood, weakening them. Mice can take over boxes. Snakes and raccoons can raid nests. Unhatched eggs can break, and nestlings can die, and rot or attract pests. (Don't panic - you can learn to deal with these problems.)
Unmonitored boxes can negatively impact native bird reproduction in other locations. For example, if House Sparrows are allowed to breed in YOUR boxes, they may attack and kill eggs, nestlings and adult native birds nesting in other locations.
Data gathered by citizen scientists during nestbox monitoring is needed to increase our understanding of the natural world, and learn more about how to help native birds.
Won't the birds abandon the nest if I monitor it ?
Bluebirds and Tree Swallows are remarkably tolerant of humans, and will not abandon the nest as a result of normal monitoring. Most song birds have a limited sense of smell. Some other birds like Titmice are more shy (See differences). Because of this, it's important to monitor as quietly and quickly as possible, and then move on so as not to stress the birds. You do WANT the parents to be protective of the nest (to scare off humans and predators that don't have your good intentions) so it's not good for them to become too accustomed to invasion.
It's also important to keep track of when the eggs were laid or hatched, to avoid monitoring when the nestlings are older, as they could prematurely leave the nest before they are able to fly or cope with the great outdoors.
The parents (especially Tree Swallows) may swoop at you to protect their nest. That is a good thing - you want them to be defensive. But it can be scary at first. Don't worry, they won't actually connect, although they may come close (e.g., 2 feet). The ONLY time I ever heard of a bluebird monitor getting hit was accidental - the man stooped over to pick something up and then stood up quickly and the Tree Swallow was unable to avoid him. If you are really scared, wear a hat or carry a broom.
How often and when should I monitor?
It depends on how serious pest or predator problems are in your area, how much data you want to collect, and how much time you have available. Once an hour is way too disruptive. Every four to five days, or once or twice a week is typical during active nesting season. A lot can happen over that time period. But do not pester them - you don't want them to go elsewhere.
You only need to monitor during nesting season (spring and summer).
Try to monitor during calm, dry weather conditions to reduce chilling nestlings or eggs. An exception is when it rains for days - you should check to see if the nest is dry and consider providing supplemental mealworms to the parents for feeding (see more on hypothermia.) If it's less than 50 °F out, avoid opening the box unless you suspect something is wrong. The best time to monitor is afternoon. Don't monitor in early morning during egg laying, or towards dark.
Don't monitor side/front opening boxes after bluebird nestlings are 12-14 days old, to avoid premature fledging. If you observe parents feeding the babies regularly during the day, that is generally a sign that things are okay.
If babies do prematurely fledge, and are unable to fly, try to capture them (throw a towel over them) and return them to the box. Stuff a sock in the hole until they calm down (maybe 15 minutes.) Sometimes they will jump right back out. If possible install a 1" hole restrictor so parents can continue to feed, but babies can not exit, and remove the restrictor when fledging would typically occur. See more info.
Make your presence known. Startling an incubating female could result in damage to eggs. Approach the box, call out or whistle and tap gently on the side, with your face away from the hole (in case a brooding bird flies out.) Open the box slowly, and quickly peek inside. Be careful not to let eggs/chicks fall out! Close it slowly - a sitting female may suddenly try to exit the box and you would not want to injure it while closing the door.
Spend less than a minute checking the nest to avoid stressing the occupants and chilling eggs/nestlings.
A car mechanics mirror is helpful to look into the nest without disturbing it. If you have a small round one that fits in a hole, place the dental mirror just inside the entrance hole and then use a pen light to bounce light off of the mirror to illuminate the nest.Don't feel around in a nest you can't see unless you want a surprise (snakes, mice, flying squirrel bites, black widows.)
Don't touch eggs while monitoring. Some, especially chickadee eggs, are very fragile. Also oil from hands could inhibit hatching.
Don't disturb the nest while monitoring (with the exception of a nest change). If you move it around, eggs or babies could get lose/fall underneath the nesting material and die.
Limit photographs that might distress nest occupants. Cavity nesters are used to the dark, and since we don't know whether baby bird's developing eyes could be affected by a flash, avoid using one with nestlings.
Move away from the box, and then make a note on a log of what you see - what kind of nest, how many eggs, how many nestlings, any evidence of problems, etc. (Note: Tree Swallows and some other nesters may refuse to budge while incubating - leave them be.)
If you are sure all eggs have hatched more than 72 hours earlier, remove unhatched eggs so they don't break and make a mess (sometimes the parents will remove unhatched eggs.)
Make sure any baffles are in place to prevent predators for gaining access to the box.
Close the box securely.
If yellow-jackets (a wasp) are common in your area, watch the box for a minute or two before opening it.
After babies have fledged, clean out old nesting material to encourage another brood. Also, detritus in old nests can attract fire ants, and the nests are sometimes infested with mites or blow fly larvae. I brush out the box, scrape it with a putty knife, and then spray it with a pre-mixed dilute solution of Chlorox (10%), open up the box and let it dry for a day, and then close the door. Do NOT breathe in dust/dried fecal matter (stay upwind, consider wearing a dust mask). Put nests in a baggie, and dispose of them in the trash to avoid attracting predators.
At the end of the season, clean out any boxes by removing old nesting material. Do any needed repairs (caulking, re-nailing, staining exterior, etc.) Leave boxes up all winter for roosting. If mice tend to use boxes during the winter, you will need to clean the boxes out in the early spring also.
What kind of equipment will I need?
The following items will come in handy:
deep bucket (e.g., cat litter or spackle) or canvas bag to hold everything
ziplock plastic bag (e.g., to dispose of used or blow fly infested nests or other problems liked dead birds)
spatula, metal putty knife, paint scraper, wood lath, or "hive" tool (to scrape out boxes or squash wasps)
screwdriver if your boxes are screwed shut (make sure you have the right bit(s)
telescoping car mechanics inspection mirror to look into nests that are high, without disturbing them (available at Amazon.com - e.g, K-D Tools 2108 Telescoping Mirror - or Ace Hardware). You may need to bounce the light from a flashlight off it.
roll of fishing line (to deter House Sparrows) and scissors
spray bottle of 10% bleach solution (to spray mouse nests before removal, and to disinfect box interior after removing used nests)
Hole restrictors (in case a hole has been enlarged, or you want to protect smaller species.)
Spare screws
Optional items that might be useful:
duct tape (for emergency repairs)
gloves (for handling mouse nests, dead birds, etc.)
camera
step stool for high boxes
It's useful to keep a paper/spreadsheet that you can print out that tracks activity in each box, or one that at least shows last week's record. Another option is a handheld tape recorder/PDA.
Buy a good book on bluebirds (e.g., The Bluebird Monitor's Guide) that explains how to identify birds, nests and eggs, correctly monitor an active nestbox, and prevent/deal with problems.
A man's interest in a single bluebird is worth more than a complete but dry list of The basic rules for studying nesting birds, therefore, are as follows: disturb as little as possible; preferably examine nests only when the owners are absent; be as quick as possible; and at all times exercise the greatest care and caution, remembering that a little carelessness can bring about the accidental destruction of nest and brood.
- A Guide to Nests, Eggs and Nestlings or North American Birds, by Baicich and Harrison, 1997
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