Tag Archives: hatch

HATCHING

© elfruler 2018, 2021
with thanks to Donna Young

The avian egg is a marvel of nature, a self-enclosed and perfectly effective living environment for the developing bird embryo. The shell  is sturdy but flexible, hard but porous. The egg contains all that is necessary to enable a small and weak organism to develop into a chick with all its parts and enough strength and skill to break through and emerge into the outside world. Here is an account of the many factors involved in a chick’s hatching.

Inside the shell

  • The eggshell is a complex structure of hard calcium carbonate crystals interwoven with collagen fibers and coated by a thin layer of crystalline calcite and smooth protein cuticle. The structure is sturdy to protect the developing embryo, yet permeable with microscopic pores that allow oxygen to pass into the egg and carbon dioxide and water vapors to pass out.
  • Two soft keratin membranes line the inside of the shell, both formed in the isthmus of the oviduct a few hours after fertilization. These membranes facilitate the exchange of oxygen, carbon dioxide, and water through the hard shell. The outer membrane becomes fused to the inside of the shell near the time of hatching, and the thinner membrane lines the inner surface of the outer membrane. A gap between the two membranes forms a small air cell in the large (blunt) end of the egg, which will become very important when hatching is near.
  • A third membrane is adjacent to the inner shell membrane, the chorioallantoic membrane (CAM), which surrounds the embryo and effects the exchange of oxygen and carbon dioxide via a network of blood capillaries connecting it to the embryo. It also collects wastes that cannot be evaporated through the shell from the growing embryo, which it sheds after the egg hatches. The CAM is homologous to the mammalian placenta.
  • The embryo is attached to the yolk sac — which contains fat and protein to feed the growing chick — by a cord, the umbilicus, leading into the abdominal cavity.
  • The yolk sac is greatly reduced in size by hatching time. Now the egg weighs less than when it was laid because it has absorbed and metabolized fats from the yolk and lost evaporated water through the shell. At hatch a Bald Eagle egg might weigh 91-102 g (3.2-3.6 oz.), as opposed to 113-127 g (4-4.5 oz.) when laid.
  • The eggshell itself is much thinner at hatch than when the egg was laid because the chick has absorbed much of the shell’s calcium into its developing bones.
  • Starting about a third of the way through 36-39 days of the embryo’s growth in the egg, an “egg tooth” or “pipping tooth,” a small, hard, sharp protuberance of calcified keratin on the beak’s upper mandible, begins to develop. Here is a closeup of the egg tooth on a hatchling eaglet at the Institute for Wildlife Studies. The egg tooth gradually wears away within a couple of weeks after hatch.
  • A muscle in the back of the chick’s neck (the complexus or hatching muscle) swells in response to the influx of lymphatic fluids. This muscle recedes in size after hatching (although it later plays a role in neck extension in grown eagles).

The hatching process

  • When hatching nears, the air cell in the large (blunt) end of the egg quickly expands and spreads partway down along the upper side of the egg.
  • As the embryo nears full development it takes up most of the space inside the shell – it is crowded in there! The chick has gradually rolled to curl up tightly, lying on its left side with its legs bent in the smaller end of the shell, its back against the air cell. Its head is tucked forward against its breast near the blunt end of the shell and turned to the right under its right wing. This puts the beak and the egg tooth close to the air cell. Here is a drawing of the position of the chick in a chicken egg at 20 days, just before hatching.
  • As it takes hatching position, the embryo absorbs the remainder of the yolk sac into its abdominal cavity.
  • The complexus muscle begins to contract, causing the entire body of the chick to straighten and contract, pushing the egg tooth against the air cell and piercing it. This results in what is called the internal pip. The air cell releases a small supply of oxygen and prompts the chick’s lungs and its 9 air sacs to begin functioning.
  • With its lungs now working, the chick can also begin to vocalize, as can be heard in this video of an egg just as it pips the shell at the Institute for Wildlife Studies incubation facility in 2008.
  • After the internal pipping the chick rests as its lungs learn to directly inhale oxygen and exhale carbon dioxide. At this point the blood circulation and gas exchange via the CAM (chorioallantoic membrane) are winding down and the cord that connects the CAM to the embryo begins to wither.
  • After a few hours the buildup of carbon dioxide inside the shell stimulates the complexus muscle to contract more. The head and beak begin to jerk back against the shell repeatedly and the spine and legs push against the shell, finally piercing it with the egg tooth near the blunt end of the egg. This is seen from the outside as a “pip” or tiny hole or crack in the shell, usually on the side of the shell and near the larger end of the egg (but note that the beginning of a pip is often not in view on a nest cam). This is called the external pip.
  • After the first external pip that allows outside oxygen into the egg, the chick usually rests again for several more hours while its respiratory and circulatory systems continue to adapt.
  • The external pip accelerates fluid loss inside the egg as well as in the chick’s body, which is good because a slightly reduced body mass allows the chick more room to maneuver as it pushes against the shell.
  • The pip may begin as a tiny hole that increases in size over the next few hours. Or it may begin as a cracking of tiny bits of the shell, possibly taking a star-like appearance (“starring”). As the chick pushes outward, small bits of shell may bulge from the hole, often visible in profile as the pip is turned to the side. The chick’s legs flex and contract and the egg tooth pokes and scrapes the shell, creating larger holes and cracks. The chick’s beak, pipping tooth, and head might be visible through some of the cracks. The enlarged complexus muscle at the nape provides cushioning and support during this shell-breaking process.
  • As it pushes against the shell, the chick may begin to rotate, usually counterclockwise, perhaps halfway or more around the inside, until a part of the shell, often a roundish disc at one end, or a “cap,” separates and breaks the shell apart. This has led to the term symmetrical hatching, referring to the more or less symmetrical shape of both the broken-off cap and the rest of the egg. Symmetrical hatching is the norm for most avian species.
  • However, as observers of Bald Eagle cams over the years have noted, not all hatches result in a symmetrical breakup of the shell; in fact, some hatches look downright chaotic and messy. Sometimes the first external pip seems to simply grow in size until the chick breaks through the gap. Sometimes the shell membrane holds the shell together so that it does not break apart cleanly and the chick has to push through both shell and membrane to be free.
  • The hatching process is strenuous and can take up to 72 hours to complete.  The chick rests inbetween efforts to break through the shell.
  • Most biologists and observers consider the egg to be “hatched” when the chick fully emerges free from the shell.
  • The new hatchling is covered with a thin layer of downy feathers – its natal down – which is damp from the fluids inside the shell, matted against its mostly pinkish skin (but dark gray around the eyes). The down will dry out to a soft light gray color within a couple of hours.
  • The hatchling weighs about three-quarters of the weight of the egg when first laid about 37-39 days before – decreasing from about 113-127 g (4-4.5 oz.) to about 85 g (3 oz.). (Sizes vary with latitude – larger in the north than in the south – and also with hatch order – first eggs in a clutch are larger than subsequent eggs.)
  • After hatching the chick will lie in the nest resting for several hours. It will roll about a little, and the wings, legs, neck, and head may jerk spasmodically from time to time. Its breathing can be seen, and it will let out some tiny cheeps, which can be both heard and seen.

Parental behavior during hatching

  • The parents are aware of the hatching when they hear the chick’s vocalizations and possibly also its pecking at the shell. The incubating adult may stand above or to the side of the egg and lean in or cock its head, seeming to listen. Parents may chirp softly to the chick, or champ or click their beaks, perhaps another attempt to communicate.
  • They might continue to gently nudge the hatching egg and even the emerging chick with their beak.
  • They may exhibit restlessness in the egg cup, rising to check the eggs every few minutes, circling the cup, leaning in often to listen. They often pull soft nesting material in toward the nest cup (sometimes building a wall between the cup and the viewers!).
  • Both parents, but especially the male as the female does more of the incubating, may bring food to the nest in anticipation of both the chick’s and the mother’s need for food as brooding begins.
  • The parents do not assist the chick in breaking the shell because they could damage the still fragile blood vessels in the CAM. They may move shell fragments away from the hatching egg.

Post-hatching

  • Bald Eagle hatchlings are “semi-altricial,” which means they are nearly helpless when they hatch, with limited motor skills and strength, entirely dependent on parents for food and warmth, and confined to the nest (“nidicolous” – “nest inhabiting”). All raptors are semi-altricial and must spend several weeks being cared for by their parents in the nest before they fledge and are capable of fending for themselves.
  • Raptors are not considered fully altricial (like songbirds and parrots) because their eyes are open at hatch, they are covered with downy feathers, and they have some mobility.
  • At the other end of the developmental spectrum from altricial are “precocial” chicks, like geese, ducks, swans, chickens, quail, etc., which are capable of walking (and often swimming) and thermoregulating soon after they hatch. They are “nidifugous” (“nest fleeing”), meaning they leave the nest almost immediately after hatching.
  • In the days before it hatched the eagle chick has absorbed the yolk sac into its body, whose nutrients feed it in the few hours before and after hatch. It will not need to be fed by its parents for several hours.

Clearly, hatching is a complex process, and most of the time it ends successfully.  Sometimes, though, things can go wrong.  This page surveys reasons why an egg might fail to hatch.

Here is a compilation video of the hatch of the first eaglet at the West End nest on Catalina Island on 20 March 2018.
Detailed description of the development of a chicken embryo from fertilization through hatch, with great drawings and images.

References

  • Bond, G.M., V.D. Scott, and R.G. Board 1986. Correlation of mechanical properties of avian eggshells with hatching strategies. Proceedings of the Zoological Society of London (A) 209:225-237.
  • Bond, G.M., R.G. Board, and V.D. Scott 1988.  An account of the hatching strategies of birds.  Biological Review 63:395-415.
  • Bortolotti, G.R. 1984.  Physical development of nestling Bald Eagles with emphasis on timing of growth events. Wilson Bulletin 96:524-542.
  • Deeming, D.C. 2002.  Avian Incubation: Behaviour, Environment, and Evolution (Oxford and New York: Oxford University Press).
  • Deeming, D.C. and S.J. Reynolds, eds. 2015.  Nests, Eggs, and Incubation: New Ideas about Avian Reproduction (Oxford: Oxford University Press).
  • Drent, R. 1973.  The natural history of incubation. In Breeding Biology of Birds: Proceedings of a symposium on breeding behavior and reproductive physiology in birds, Denver, Colorado, February 1972, ed. D.S. Farner (Washington, DC: National Academy of Sciences):262-322.
  • Fox, N. 1995.  Understanding the Bird of Prey (Surrey, British Columbia and Blaine, WA: Hancock House Publishers).
  • Gill, F.B. 2007.  Ornithology, 3rd ed.  (New York: W. H. Freeman and Company).
  • Hamburger, V. and R. Oppenheim 1967. Prehatching motility and hatching behavior in the chick. Journal of Exp. Zool. 166:171-204
  • Lovette, I.J. and J.W. Fitzpatrick, eds. 2016.  The Cornell Lab of Ornithology Handbook of Bird Biology, 3rd ed. (Chichester, West Sussex: John Wiley & Sons, Ltd.
  • Oppenheim, Ronald W. 1972. Prehatching and hatching behaviour in birds: a comparative study of altricial and precocial species. Animal Behaviour 20:644-655.
  • Podulka, S., R.W. Rohrbaugh, Jr., & R. Bonney, eds. 2004.  Handbook of Bird Biology, 2nd ed. (Ithaca, NY: The Cornell Lab of Ornithology).
  • Proctor, N.S. and P.J. Lynch 1993.  Manual of Ornithology: Avian Structure & Function (New Haven and London: Yale University Press).
  • Sharpe, P. 1995.   Guide to Bald Eagle Egg Incubation and Chick-Rearing.  Institute for Wildlife Studies.
  • Starck, J. M. and R.E. Ricklefs, eds. 1998.  Avian Growth and Development Evolution within the Altricial-Precocial Spectrum (New York and Oxford: Oxford University Press).

 

CLUTCHES, EGGS, and FLEDGES

These numbers come from all Bald Eagle nests for which I have records, including those observed on camera and from the ground.  See here for a list of these nests.  Excluded from these data are nests in aviaries where non-releasable eagles are provided with food, medical, and other care (Carolina Raptor Center in NC and American Eagle Foundation in TN).

Click on the chart to enlarge.

© elfruler 2018

When Will That Egg Hatch?

I’ve compiled and analyzed data from wild Bald Eagle nest cams from 2006-2016 concerning how long it takes for an egg to hatch.

In some ways the numbers support what veteran cam watchers have come to know about parents’ incubation behavior, delayed hatching of the first egg, and how close together hatches can occur in comparison to the minimum 3 days between egg-layings.

For instance, the first egg almost always takes longer to hatch than later eggs. Observations from these nests give us a pretty good idea of how much longer.

And hatches can occur as few as 4 hours apart. But for which eggs in a clutch?  The data tell us.

The data also show some more subtle facts, such as differences in hatch timings between a 2-egg clutch and a 3-egg clutch.

There are some unexpected numbers, such as the average time overall between when an egg is laid and when it hatches.  It’s 36.5 days.  Not 34 or 35.

In fact, the shortest hatch time on record at these wild Bald Eagle nests was 34 days 11 hours 1 minute after the egg was laid.  And that fast time is an outlier in the data.

The longest time on record was 40 days 12 hours 17 minutes.

And whether a nest is in a northern climate or a southern climate seems to make no difference in whether hatching is delayed.

Go here to take a deep dive into the data and my analyses.

HATCH TIMINGS

This page presents data about times from egg-laying to hatch and  times between hatches recorded at wild Bald Eagle nest cams from 2006-2016.

The information here comes from JudyB’s charts, the Hancock Wildlife Forum, the Channel Islands EagleCAM Forum, nest cam websites, and my own observations. Scroll down for charts giving the raw data.

Determining the exact time of hatch is difficult for several reasons:
  • A hatch may not be visible on the cam because the camera angle may not give a clear view into the nest cup, or an incubating parent, another egg or nestling, or nesting material may obscure the view.
  • The online video stream may not have an embedded timestamp, or if present it may not be accurate.
  • Most experts agree that a hatch has occurred when a chick is completely free of the shell, but some observers may record a time when the chick is only partially out of the shell.

Thus time of hatch may be approximate, or reported times may vary from one viewer to another. I have attempted to restrict my analysis to data that appear to be as reliable as possible, which includes dates and times for 44 breeding seasons at 31 nests with 2-egg clutches (N=44), and 28 breeding seasons at 20 nests with 3-egg clutches (N=28). In my judgment the overall analysis is plausible given the size of the sampling and consistency among the data.

General observations

Time from egg-laying to hatch among all 72 clutches:

  • The average time was exactly 36.5 days (36 days 12 hours).
  • The shortest time was about 34.5 days (34 days 11 hours 1 minute).
  • The longest time was about 40.5 days (40 days 12 hours 17 minutes).

The interval between egg-laying and hatch almost always decreases for successive hatches in a clutch.

In 2-egg clutches, Egg 1 takes on average about 1.4 days longer to hatch than Egg 2:

In 3-egg clutches, Egg 1 takes on average almost 2 days longer to hatch than Egg 2 and almost 2.5 days longer to hatch than Egg 3:

The data also show that it takes longer for an eagle to lay a complete clutch of eggs (click here for data on egg-laying) than it does for those eggs to hatch:

The reason for these differences can be found in the incubation behavior of the parents.
  • Bald Eagles’ eggs hatch successively in the order in which they were laid, called asynchronous hatching.
  • The first chick to hatch will be larger and more developed than its sibling(s), which gives it an advantage in the competition for food in the nest.
  • To help mitigate this disparity, the parents usually incubate the first egg intermittently until the second egg is laid, which slows the development of the embryos of the earlier eggs.
  • This phenomenon is sometimes referred to as “delayed incubation,” but the parents usually do incubate most of the time, so it is actually the hatching that is delayed. A better description of the behavior might be “intermittent incubation.” Scientists use the term parental attentiveness in reference to the amount of time parents devote to incubating.
  • Parents gradually increase their attentiveness until the clutch is complete.
  • Since later eggs are incubated more consistently than earlier eggs, their development progresses more quickly and they hatch in less time.

Another way to see the effects of parental attentiveness on different eggs in a clutch is to consider the intervals between hatches.  In 3-egg clutches, because Hatch 1 is usually delayed and Hatch 3 is not, the interval between Hatches 1 and 2 is considerably shorter than the interval between Hatches 2 and 3:

  • The shortest hatch-to-hatch time on record was 3 hours 57 minutes between Hatch 1 and Hatch 2 in a 3-egg clutch.
  • The longest hatch-to-hatch time on record was 99 hours 42 minutes between Hatch 2 and Hatch 3 in a 3-egg clutch.
Geography does not appear to play a predictable role in incubation behavior.
  • One might expect that eggs in colder northern climates would be incubated more regularly than those in warmer southern climates. The data do not bear this out.
  • Longer incubation times for first eggs, indicating partial parental attentiveness, occur in both colder climates including Pennsylvania, Maryland, Minnesota, Iowa, and British Columbia, and in warmer climates including Florida, Virginia, and the Channel Islands off the California coast.
  • Conversely, shorter incubation periods for first eggs, indicating close to full parental attentiveness, occur both at nests in colder climates, including Wisconsin, Minnesota, Iowa, New Jersey, and British Columbia, and in warmer climates, including Florida, Virginia, and the Channel Islands.
  • But local climate is not solely a function of latitude. Other conditions such as elevation above sea level, proximity to a large body of water like an ocean or lake, precipitation and humidity, rural or urban habitat, and changeable weather conditions from year to year certainly affect both the dates of egg-laying and the incubation behavior of parents.
The charts below show the information collected.

You can sort on a column by clicking its heading. Nest codes used here are listed in this chart. All times are local nest time and are given in 24-hour format without a colon (0000 = midnight, 1200 = noon).

Abbreviations:
h = hour
m = minute
d = day
< = before or by (not included in calculations)
~ = approximately (not included in calculations)
strikeout = unhatched eggs
italics = nestlings that died before fledge

2-Egg Clutches
NESTEGG 1Time E1-H1HATCH 1EGG 2Time E2-H2HATCH 2Time H1-H2
WI e4k3/2/12 163035d12h49m4/7/12 06193/5/12 185435d10h26m4/10/12 062003d00h01m
BC har3/24/15 204835d19h22m4/29/15 16103/28/15 180935d08h25m5/3/15 023403d10h24m
BC har4/4/13 201035d21h50m5/10/13 18004/8/13 194435d18h55m5/14/13 1439
starv		03d20h39m
BC har4/3/16 202135d22h06m5/9/16 18274/7/16 170735d18h04m5/13/16 111103d16h44m
FL nef11/14/13 134236d02h44m12/20/13 162611/17/13 134835d10h21m12/23/13 000802d7h42m
FL nef11/16/15 134936d03h29m12/22/15 171811/19/15 164235d02h09m12/24/15 185102d1h33m
FL swf11/17/13 163736d07h09m12/23/13 2346
infection?		11/20/13 181834d16h03m12/25/13 102101d10h35m
FL swf11/26/12 134436d09h00m1/1/13 224411/29/12 1838<35d03h16m1/3/13
2149-2154
CA zSC3/2/12 184136d10h51m4/8/12 06323/6/12 0026<4/11/12 am
MN bnd3/1/16 174036d13h40m4/7/16 08203/4/16 182635d11h06m4/9/16 063201d22h12m
CA zPH2/24/08 132936d16h46m4/1/08 07152/27/08 17004/2/08 1615?
or <4/3/08 0631
CA trt2/12/11 164936d16h54m3/21/11 10432/15/11 164536d17h30m3/24/11 111503d00h32m
BC hrn3/22/11 194436d17h55m4/28/11 13393/26/11 152336d00h28m5/1/11 155103d02h12m
WI val3/27/14 160836d18h52m5/3/14 1100
GHOW pred		3/30/14~1950~35d23h40m5/5/14 193002d08h30m
FL swf11/19/14 140736d22h52m12/26/14 125911/22/14 161634d19h12m12/27/14 112800d22h29m
BC wht3/13/12 153236d23h26m4/19/12 14583/16/12~2010~35d17h30m4/21/12 134001d22h42m
VA ccb2/8/12 174437d00h46m3/16/12 19302/11/12 181735d12h14m3/18/12 073101d12h01m
MD blk1/26/08 155037d01h47m3/3/08 17371/29/08 or
1/30/08<0656		3/5/08 063301d12h56m
IA dav2/7/13 143037d02h10m3/16/13 17402/10/13 18083/18/13 am
TN har2/18/15 170437d02h30m3/27/15 20342/21/15 182636d11h52m3/30/15 071802d10h44m
BC sid3/4/10 183537d10h45m4/11/10 06203/7/10 1956
raven pred
CA cTH2/17/11 203137d10h53m3/27/11 08242/21/11 2323
broke
CA cTH2/17/10 184637d12h29m3/27/10 08152/21/10 190034d23h43m3/28/10 194301d11h28m
TN har2/10/13 174537d12h38m3/20/13 07232/13/13 1856~35d22h04m3/21/13~1800
ME br23/8/10 160637d12h47m4/15/10 05533/11/10 1807?35d20h29m?4/16/10 153601d09h43m
BC wht3/13/15 165737d13h28m4/20/15 06253/16/15 2019<35d11h37m4/21/15<0756
FL swf
new M		12/19/15 162537d14h58m1/26/16 072312/22/15 174036d04h59m1/27/16 223901d15h16m
CA hum3/17/15 150337d16h50m4/24/15 07533/20/15~1930~36d04h44m4/26/15 001401d16h21m
NC jor2/28/14 185837d18h04m4/7/14 14023/4/14 18414/9/14 pm?
CA cWE2/28/09 173337d18h48m4/7/09 13213/3/09 1758~35d21h42m4/8/09 1640?
WV shp2/6/13 180937d19h29m3/16/13 14382/9/13 181535d20h18m3/17/13 153301d00h55m
WV shp
new M		2/5/12 173437d21h04m3/14/12 15382/8/12 2311<36d07h09m<3/16/12 0720
NC crc1/18/12 160737d21h05m2/25/12 13121/21/12 pm?
no hatch
MD blk1/11/12 144437d21h38m2/18/12 1222
ad BAEA pred		1/14/12 16092/18/12 pm
ad BAEA pred
GA ber1/6/15 170037d23h27m2/13/15 16271/9/15 1906<36d11h10m2/15/15<0616
TN har1/27/16 175238d01h38m3/5/16 19301/30/16 185535d21h36m3/6/16 163100d21h01m
GA ber1/7/16 172838d02h6m2/14/16 19341/10/16 191836d18h54m2/16/16 141201d18h38m
BC dl33/1/15 142338d02h8m4/8/2015 17313/4/15 1427
no hatch
BC wht3/13/11 163138d02h23m4/20/11 18543/16/11 202736d00h41m4/21/11 210801d02h14m
BC dl23/28/14 160838d05h35m5/5/14 21433/31/14 155735d18h40m5/6/14 103700d12h54m
CA cWE2/11/16 224238d11h36m3/21/16 11182/15/16 184236d12h45m3/23/16 082701d21h09m
BC dl2
new nest		3/10/16 155538d13h26m4/18/16 06213/13/16 133536d06h30m4/18/16 200500d13h44m
PA han2/18/16 151339d03h12m3/28/16 19252/21/16 1615
no hatch
TN jns2/10/16 070839d04h57m3/20/16 13052/13/16 1710?
FL nef11/16/14 1252~36d19h43m12/23/14~083511/19/14 132636d01h30m12/25/14 1456
NJ duk2/18/16 1615~36d23h45m3/26/16~17002/21/16 173535d14h6m3/28/16 0841
CA zPH2/25/10 1736<36d12h58m<4/3/10 07342/28/10 145235d19h27m4/5/10 1119
ME br13/16/14 1355<37d16h09m<4/23/14 06043/19/14 170535d23h37m4/24/14 1642
starv?
MT lib3/16/09 1825<38d12h55m<4/24/09 07203/20/09 165036d17h34m4/26/09 1024
BC dl23/3/11 am4/11/11 13133/6/11 111036d22h4m4/12/11 1014
CA cTH2/19/12 1831< 3/26/12
hatch fail?		2/22/12 202735d13h14m3/29/12 1041
fox pred
BC dl2~3/3/12< 4/11/12 06153/6/12 171735d17h12m4/11/12 1129
CA zPH
new nest		3/6/12 1358
broke		3/9/12 140135d02h6m4/13/12 1707
CA cTH2/15/13 2257
broke		2/18/13 220034d17h28m3/25/13 1628
BC dl23/7/13 pm
no hatch		3/10/13 153436d21h10m4/16/13 1244
GA ber1/14/14 1512
no hatch		1/17/14 190135d16h19m2/22/14 1120
CA cWE
new F		2/23/15 1633
broke		2/26/15 193337d11h29m4/5/15 0802
infection
© elfruler 2017
3-Egg Clutches
NESTEGG 1Time E1-H1HATCH 1EGG 2Time E2-H2HATCH 2EGG 3Time E3-H3HATCH 3Time H1-H2Time H2-H3Time H1-H3
IA dav2/11/12 145336d15h32m3/19/12 07252/14/12 1333~35d19h03m3/21/12~09362/17/12 163535d16h55m3/24/12 103005d03h05m
MN bnd3/7/14 164936d21h22m4/13/14 15113/10/14 182835d23h48m4/15/14 18163/13/14 220036d08h20m4/19/14 0620
weather		02d03h05m03d12h04m05d15h09m
IA dnn3/11/16 142936d21h50m4/17/16 13193/14/16 1428<35d13h51m4/19/16 <0419
poison		3/18/16 084136d00h33m4/23/16 091405d19h55m
IA dec2/25/10 192636d23h07m4/3/10 19332/28/10 221335d16h58m4/5/10 16113/5/10 18504/9/10 1730 or
4/10/10 0834		01d20h38m
IA dec2/18/15 180737d00h32m3/27/15 19392/21/15 190135d12h15m3/29/15 08162/25/15 185735d13h46m4/2/15 094301d12h37m04d01h27m05d14h04m
IA dec2/23/11 173337d08h06m4/2/11 02392/26/11 184235d11h20m4/3/11 07023/2/11 184734d11h01m4/6/11 064801d04h23m02d23h46m04d04h09m
BC sid3/1/09 171137d13h01m4/8/09 0712<3/5/09 07174/10/09 07593/8/09?4/14/09 075602d00h47m03d23h57m06d00h44m
IA dec2/23/14 165537d15h27m4/2/14 09222/26/14 173336d04h56m4/3/14 23293/2/14 184335d15h02m4/7/14 104501d14h07m03d11h16m05d01h23m
BC sid3/7/11 154437d17h04m4/14/11 09483/10/11 164836d13h38m4/16/11 07263/14/11 180436d00h12m4/19/11 181601d21h38m03d10h50m05d08h28m
NJ duk2/28/11 140037d17h04m4/7/11 08043/3/11 150936d15h05m4/9/11 07143/6/11 <161601d23h10m
CA trt2/6/15 153637d17h25m3/16/15 10012/9/15 154436d01h27m3/17/15 18112/12/15 165635d13h00m3/20/15 065601d08h10m02d12h45m03d20h55m
MN dnr1/25/16 151837d17h32m3/3/16 08501/28/16 134536d05h49m3/4/16 19341/31/16 1632~35d13h48m3/7/16~062001d10h44m
VA nbg2/3/11 144937d19h36m3/13/11 11252/6/11 162536d18h35m3/15/11 12002/9/11 175535d18h35m3/17/11 133002d00h35m02d01h30m04d02h05m
BC laf3/13/13 161037d20h26m4/20/13 12363/16/13 162535d22h27m4/21/13 14523/19/13 162634d20h11m4/23/13 1237
hatch fail		01d02h16m
VA riv2/16/16 152937d21h11m3/25/16 13402/19/16 152536d02h26m3/26/16 18512/23/16 <2330
no hatch		01d05h11m
CA trt2/15/10 161538d02h07m3/25/10 19222/18/10 163236d00h33m3/26/10 18052/21/10 184535d13h10m3/29/10 085500d22h43m02d14h50m03d13h33m
BC wht3/16/14 163738d12h17m4/24/14 04543/19/14 184035d21h49m4/24/14 16293/22/14 2003
accid broke		00d11h35m
MN dnr2/14/14 150038d14h47m<3/25/14 0647
injury		~2/17/14<3/26/14 1716~2/20/143/30/14 0630
IA dec2/17/12 194738d16h33m3/27/12 13202/20/12 210636d10h44m3/28/12 08502/24/12 200535d06h10m3/31/12 031500d19h30m02d18h25m03d13h55m
BC laf3/15/14 163938d18h27m4/23/14 11063/18/14 1600
hatch fail		3/21/14~1900~35d13h28m4/26/14 082802d201h22m
WV shp2/17/14 175438d20h56m3/28/14 15502/20/14 1819<36d12h53m< 3/29/14 0812<2/24/14?05454/1/14 am
CA trt2/6/09 180038d21h09m3/17/09 16092/9/09 171737d13h26m3/19/09 07432/13/09 pm or 2/14/09 am3/22/09 am01d15h34m
VA nbg2/10/09 162538d21h41m3/21/09 15062/13/09 170536d14h43m3/22/09 08482/17/09 120835d18h03m3/25/09 071100d17h42m02d22h23m03d16h05m
VA nbg1/31/10 141438d22h56m3/11/10 13102/3/10 1150~37d12h11m~3/13/10 00012/6/10 1229~35d11h32m~3/14/10 0001
OH snd2/27/16 165039d15h07m4/7/16 08573/1/16~1800~39d13h05m4/10/16 08053/4/16<21294/15/16~111502d23h08m
CA cWE2/23/11 174139d17h16m4/4/11 11572/26/11 1840<37d10h59m?4/5/11<06393/2/11 2030?<35d08h49m?4/7/11<0619
CO fsv2/14/15 181739d18h16m3/26/15 13332/17/15 181736d22h13m3/26/15 1730
weather		2/20/15 195836d10h54m3/29/15 075200d03h57m02d14h22m02d18h19m
CA cWE2/22/13 181040d12h17m4/4/13 07272/25/13 205737d17h32m4/4/13 15293/1/13 1655<36d12h20m4/7/13<061500d08h02m
PA pit2/19/14 1645~36d20h51m3/28/14~14362/22/14 161835d13h59m3/30/14 07172/25/14 183935d21h15m4/2/14 165403d09h37m
OK seq12/17/11~1600~37d18h47m1/24/12 104712/20/11 162935d20h27m1/25/12 125612/23/11 pm1/29/12 1638
weather		01d02h09m04d03h42m05d05h51m
CO fsv<2/17/09 0658~37d22h41m3/27/09 0539
weather?		2/19/09 180035d21h00m3/27/09 1600
weather?		<2/24/09 06203/31/09 1549
weather?		00d10h21m03d23h49m04d10h10m
NJ duk2/17/14 1534~39d13h26m3/29/14~06002/20/14~1400~36d18h01m3/29/14 09012/23/14 164636d13h08m4/1/14 065402d21h53m
CO fsv2/16/16~2100~40d11h23m3/28/16 0923
weather		2/19/16 2017~37d21h43m3/28/16~1900
weather		2/23/16 184736d12h58m3/31/16 0845
weather		02d23h22m
CO fsv2/17/13 1809<39d11h12m3/29/13<06212/20/13 175436d18h01m3/29/13 1255
weather		2/23/13 184636d19h01m4/1/13 1447
weather		03d01h52m
CA cWE2/18/12 2024<39d14h04m3/29/12<11282/22/12 183736d10h58m3/30/12 06352/26/12 1752~36d11h28m4/3/12~0620
WV shp<2/4/08 09173/13/08 02392/6/08 200036d10h25m3/14/08 07252/10/08 053036d00h22m3/17/08 065201d04h46m02d23h27m04d04h13m
VA nbg
clutch 2		3/16/08
broke		3/19/08
broke		3/22/08 122036d03h18m4/27/08 1538
CA zSC2/1/16 <1409
broke		2/4/16<19013/12/16 am2/7/16 181935d16h27m3/14/16 1146
OH avn2/26/16 20454/5/16 am3/1/16 183536d15h22m4/7/16 1057<3/5/16 am4/11/16 am
© elfruler 2017

© elfruler 2016, 2017

BREEDING

This menu item tracks the stages of the Bald Eagle breeding season from the formation of a pair bond through the incubation and hatching of eaglets.  Pages will cover (links are added as pages are published):

Click here for pages about eaglet growth and development from hatch through fledge.  (See Menu item “Eagle Growth.”)

© elfruler 2017-2018

THIS WEBSITE IS DEVOTED TO THE BALD EAGLE

An extraordinary enterprise in citizen science began in 2006 when the first video cameras looking into Bald Eagle nests were live-streamed on the web by the Hancock Wildlife Foundation (HWF) and the Institute for Wildlife Studies (IWS).   Other organizations and individuals followed suit in subsequent years, so that currently over 50 nests are streamed online.  Over time millions of observers have tuned in to nests criss-crossing the continent from Alaska to Florida, southern California to Maine. The nest cams have provided wonder, entertainment, sometimes anguish, and most importantly, education about the breeding behavior of Bald Eagles.

Researchers have begun to appreciate the contributions these intimate observations are making to our knowledge.  Over a decade of information has been collected by armies of careful and objective volunteer viewers, including many who have tracked and logged their observations in forums, chat rooms, social media, and nest cam web sites, often richly supplemented by screen captures and videos.

Those observations, including my own, form the foundation of the information I present on this website.  The site is in constant development, with new pages being added as time goes on and pages are updated and edited to reflect additional or corrected information.  I hope that users will find this site educational and perhaps entertaining.

Please respect my copyright of everything on this website. Do not share anything you find here by copying and pasting, capturing a screenshot, or any other method of duplication without my explicit permission and my instructions about how to credit (Contact me). Anyone is welcome to share the site link (www.elfruler.com) or the link to whatever pages you wish to point people to. Thank you.

Bald Eagle Taxonomy

  • Kingdom: Animalia (animals)
    • Phylum: Chordata (chordates)
      • Subphylum: Vertebrata (vertebrates)
        • Class: Aves (birds)
          • Order: Accipitriformes (ospreys, kites, eagles, harriers, & hawks)
            • Family: Accipitridae (kites, eagles, harriers, & hawks)
              • Subfamily: Accipitrinae 
  • Source: Chesser, R. T., S. M. Billerman, K. J. Burns, C. Cicero, J. L. Dunn, A. W. Kratter, I. J. Lovette, N. A. Mason, P. C. Rasmussen, J. V. Remsen, Jr., D. F. Stotz, and K. Winker. 2020. Check-list of North American Birds (online). American Ornithological Society.

About me

I am a retired university professor with a Ph.D. in a discipline in the humanities.  I have been a birdwatcher for many years, and I have been fascinated by eagles since I saw my first one in flight in the early 1970s, not long after the use of DDT was banned and the population of Bald Eagles began its slow recovery.  Since 2009 I have been an avid observer of internet bird cams, and during that time I have read widely and deeply in ornithology.  For four years I volunteered for raptor rehabilitation organizations, gaining hands-on experience in the capture and rescue, medical triage and treatment, and rehabilitation of raptors and other birds.

I live in an area with a fair number of Bald Eagles, and I take every opportunity to observe them from the ground as they perch and roost, fly and soar, hunt and fish, interact with each other and their environment. I monitor several active nests during the breeding season.

I adopted the screenname “elfruler” when I began posting in forums and chatting with other viewers in nest cam chat rooms. The name reflects the meaning behind my father’s surname. But it is partly whimsical, for I have found that it seems to embody something of my personality.