Tag Archives: clutch

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

How much time passes between eggs laid?

2-eggs-in-nestThis question comes up every time a Bald Eagle lays an egg, and one person’s answer isn’t always the same as another’s. Fortunately, we now have a sizable body of data that provide a reliable answer.  Information collected from JudyB’s charts, the Hancock Wildlife Forum, the Channel Islands EagleCAM Forum, nest cam websites, and other observations give reliable dates and times for 55 nests with 2-egg clutches, 37 nests with 3-egg clutches, and 1 nest with a 4-egg clutch.

The eggs come at roughly 3-day or 4-day intervals. But the data tell us much more than that.

Go here to see the data and my analyses. And let’s have a conversation on Facebook about it.

EGG-LAYING TIMINGS

The Bald Eagle nest cams from 2007-2016 are giving us priceless new information about breeding in the wild (as opposed to captivity). We now have some real numbers to crunch. Data about egg-laying collected from JudyB’s charts, the Hancock Wildlife Forum, the Channel Islands EagleCAM Forum, nest cam websites, and my own observations give reliable dates and times for 61 breeding seasons at 29 nests with 2-egg clutches, 38 seasons at 21 nests with 3-egg clutches, and 1 nest with a 4-egg clutch. Only nests with precise timings are included in this report.

Three 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)

These data yield some general findings:

  • Most first eggs of a clutch are laid between about noon and midnight.
  • The eggs come at roughly 3-day or 4-day intervals. This is consistent with afternoon-evening layings: if another egg is not laid by the end of the third day, it is likely to come about a day later.
  • The shortest interval between one egg and the next was 68h40m or just under 3d (BC dl2 in 2016). The longest interval was 116h37m or nearly 5d (IA dec in 2010).
  • The interval from one egg to the next almost always increases with subsequent layings.
  • A particular female generally has a consistent pattern of timings. Some tend to lay eggs at 3-day intervals, others at 4-day intervals. A particular female also tends to lay at roughly the same time of day from year to year, although there are exceptions. If you sort on the Nest column in each chart you can observe the patterns and inconsistencies. See comments below the charts for further details.

2-egg clutches

  • About 82% (50 of 61 breedings) had a 3-day interval from the first to the second egg, with a mean average time of 73h21m.
  • About 18% (11 of 61 breedings) had a 4-day interval from the first egg to the second, with a mean average time of 94h34m.
  • Most females are consistent 3-day or 4-day layers from year to year (sort on the Nest column).
NESTEGG 1Time E1-E2EGG 2
BC dl23/10/16 155568h40m3/13/16 1335
CA cTH2/27/15 205769h12m3/2/15 1809
CA zPH2/25/10 173669h16m2/28/10 1452
PA han2/14/15 175470h51m2/17/15 1645
CA cTH2/15/13 2257
broke		71h3m2/18/13 2200
CA zSC2/24/13 2030
ravens pred		71h27m2/27/13 1957
ravens pred
BC dl23/28/14 160871h49m3/31/14 1557
VA riv2/12/15 1724
hatch fail		71h54m2/15/15 1718
CA trt2/12/11 164971h56m2/15/11 1645
CA zPH
new nest		3/6/12 1358
broke		72h3m3/9/12 1401
BC dl33/1/15 142372h4m3/4/15 1427
no hatch
WV shp2/6/13 180972h6m2/9/13 1815
FL nef11/14/13 134272h6m11/17/13 1348
TN har2/4/14 183572h21m2/7/14 1856
CA cWE2/28/09 173372h25m3/3/09 1758
WI e4k3/10/16 1557
juv BAEA pred		72h27m3/13/16 1724
juv BAEA pred
VA ccb2/8/12 174472h33m2/11/12 1817
FL nef11/16/14 125272h34m11/19/14 1326
BC dl23/10/15 1543
incub fail		72h38m3/13/15 1621
incub fail
MN bnd3/1/16 174072h46m3/4/16 1826
TN pgf
F & I		3/23/13 195572h51m3/26/13 2046
PA han2/18/16 151373h2m2/21/16 1615
no hatch
TN har1/27/16 175273h3m1/30/16 1855
TN har2/10/13 174573h11m2/13/13 1856
FL swf
new M		12/19/15 162573h15m12/22/15 1740
NJ duk2/18/16 161573h20m2/21/16 1735
BC sid3/4/10 183573h21m3/7/10 1956
raven pred
OR des3/24/10 2010
weather		73h21m3/27/10 2131
weather
TN har2/18/15 170473h22m2/21/15 1826
MD blk1/11/12 144473h25m1/14/12 1609
FL swf11/17/13 163773h41m11/20/13 1818
MN bnd2/28/15 155873h50m3/3/15 1748
GA ber1/7/16 172873h50m1/10/16 1918
CA cTH2/19/12 183173h56m2/22/12 2027
GA ber1/6/15 170074h6m1/9/15 1906
FL swf11/19/14 140774h9m11/22/14 1616
WI e4k3/2/12 163074h24m3/5/12 1854
MN bnd3/9/13 155274h30m3/12/13 1922
FL nef11/16/15 134974h53m11/19/15 1642
CA cWE
new F		2/23/15 1633
broke		75h2/26/15 1933
CA zPH2/25/09 142375h8m2/28/09 1731
ME br13/16/14 135575h10m3/19/14 1705
BC wht3/13/15 165775h22m3/16/15 2019
CA zPH2/24/08 132975h31m2/27/08 1700
IA dav2/7/13 143075h38m2/10/13 1808
GA ber1/14/14 1512
no hatch		75h49m1/17/14 1901
BC wht3/13/11 163175h56m3/16/11 2027
FL swf11/26/12 134476h54m11/29/12 1838
WV shp2/5/12 173477h37m2/8/12 2311
CA zSC3/2/12 184177h45m3/6/12 0026
BC hrn3/22/11 194491h39m3/26/11 1523
CA cWE2/11/16 224292h2/15/16 1842
BC har4/3/16 202192h46m4/7/16 1707
BC har3/24/15 204893h21m3/28/15 1809
MT lib3/16/09 182594h25m3/20/09 1650
CA cTH2/25/16 2206
no hatch		94h52m2/29/16 2058
no hatch
BC hrn3/30/14 2019
no hatch		94h53m4/3/14 1912
BC har4/4/13 201095h34m4/8/13 1944
NC jor2/28/14 185895h43m3/4/14 1841
CA cTH2/17/10 184696h14m2/21/10 1900
CA cTH2/17/11 203198h52m2/21/11 2323
broke
© elfruler 2017

3-egg clutches

  • About 92% (35 of 38 breedings) had a 3-day interval from the first to the second egg, with a mean average time of 72h16m.
  • About 8% (3 of 37 breedings) had a 4-day interval from the first egg to the second, with a mean average time of 93h57m. (Note the contrast with 2-egg clutches, where a larger percentage (18%) had a 4-day interval.)
  • The proportion between 3-day intervals and 4-day intervals from the second to the third egg is more balanced than with 2-egg clutches:
    • About 55% (16 of 29 nests with precise timings) had a 3-day interval, with a mean average time of 74h12m.
    • About 45% (13 of 29 nests) had a 4-day interval, with a mean average time of 96h46m.
  • As with 2-egg clutches, eagles at particular nests usually had a consistent pattern of laying from year to year (sort on the Nest column), either 3 days both between first and second eggs and between second and third eggs, or 3 days between first and second egg and 4 days between second and third eggs. Where the pattern is not consistent, possible reasons may be a change of mate (as at CA trt in 2014), inclement weather, intruders, etc.
  • The 2010 season at IA dec was unusual in that the interval between the second and third eggs, 116h37m, was  more than 20 hours longer than the next longest interval, at CA trt in 2013 (97h58m).  If the third egg-laying at IA dec in 2010 is excluded from the calculations, about 57% (16 of 28 breedings) had a 3-day interval, with a mean average time of 74h12m, and 43% (12 of 28 breedings) had a 4-day interval, with a mean average time of 94h55m.
NESTEGG 1Time E1-E2EGG 2Time E2-E3EGG 3
VA nbg1/31/10 141469h36m2/3/10 115072h39m2/6/10 1229
CA trt
new M		2/6/13 1714
disappeared		70h20m2/9/13 153497h58m2/13/13 1732
MN dnr1/25/16 151870h27m1/28/16 134574h47m1/31/16 1632
IA dav2/11/12 145370h40m2/14/12 133375h2m2/17/12 1635
IA dnn3/11/16 142970h59m3/14/16 142890h13m3/18/16 0841
CA trt2/6/09 180071h17m2/9/09 17172/13/09 pm
or 2/14/09 am
IA dec2/18/16 202871h18m2/21/16 194695h13m2/25/16 1859
infertile
BC laf3/15/14 163971h21m3/18/14 1600
hatch fail		~75h3/21/14~1900
PA pit2/19/14 164571h33m2/22/14 161874h21m2/25/14 1839
CO fsv2/17/13 180971h45m2/20/13 175472h52m2/23/13 1846
IL umr
1F & 2M		2/1/16 155771h48m2/4/16 154575h4m2/7/16 1849
VA riv2/16/16 152971h56m2/19/16 15252/23/16<2330
no hatch
CO fsv2/14/15 181772h2/17/15 181773h41m2/20/15 1958
MD blk1/13/14 1623
no hatch		72h5m1/16/14 1628<1/20/14 0847
TN pgf
I & J		2/18/16 0823
no hatch		72h7m2/21/16 0830
no hatch		96h50m2/25/16 0920
no hatch
CA trt2/6/15 153672h8m2/9/15 154473h12m2/12/15 1656
TN pgf
F & I		3/21/16 1911
no hatch		72h14m3/24/16 1925
no hatch		< 3/29/16 0730
no hatch
BC laf3/13/13 161072h15m3/16/13 162572h1m3/19/13 1626
CA trt2/15/10 161572h17m2/18/10 163274h13m2/21/10 1845
OK snr2/6/09 1547
no hatch		72h23m2/9/09 1610
no hatch		2/13/09 pm
WV shp2/17/14 175472h25m2/20/14 1819<2/24/14?0545
WV shp2/12/15 153972h27m2/15/15 160674h19m2/18/15 1825
IA dec2/23/14 165572h38m2/26/14 173397h10m3/2/14 1843
MN bnd3/7/14 164972h39m3/10/14 182875h32m3/13/14 2200
VA nbg2/10/09 162572h40m2/13/09 170591h3m2/17/09 1208
IA dec2/18/15 180772h54m2/21/15 190195h56m2/25/15 1857
CA cWE2/23/11 174172h59m2/26/11 184097h50m?3/2/11 2030?
BC sid3/7/11 154473h4m3/10/11 164896h16m3/14/11 1804
IA dec2/23/11 173373h9m2/26/11 184296h5m3/2/11 1847
NJ duk2/28/11 140073h9m3/3/11 15093/6/11 <1616
IA dec2/17/12 194773h19m2/20/12 210694h59m2/24/12 2005
VA nbg2/3/11 144973h36m2/6/11 162573h30m2/9/11 1755
BC wht3/16/14 163774h3m3/19/14 184073h23m3/22/14 2003
accid broke
CA cWE2/22/13 181074h47m2/25/13 205791h58m3/1/13 1655
IA dec2/25/10 192674h47m2/28/10 2213116h37m
4d20h37m		3/5/10 1850
TN pgf
F & I		3/27/15 2041
no hatch		93h47m3/31/15 1828
no hatch		71h7m4/3/15 1735
no hatch
OH avn2/26/16 204593h50m3/1/16 1835<3/5/16 am
CA cWE2/18/12 202494h13m2/22/12 183795h15m2/26/12 1752
WV shp<2/4/08 09172/6/08 200081h30m2/10/08 0530
© elfruler 2017

4-egg clutches

  • These are rare among Bald Eagles. From 2006-2016 only three nests with 4 eggs have been documented by direct observation (WV shp in 2010, MT cfr in 2011, and OK snr in 2013). Of those only WV shp has precise observed timings.
NESTEGG 1Time
E1-E2		EGG 2Time
E2-E3		EGG 3Time
E3-E4		EGG 4
WV shp2/2/10 2215
weather		87h57m2/6/10 1412
weather		75h34m2/9/10 1746
disappeared		92h56m2/13/10 1442
© elfruler 2017
  • The first three of the eggs were lost in snowstorms; the fourth ended in a successful fledge. Note that the timings between eggs alternate between 4-day and 3-day intervals.

© elfruler 2016, 2017. Revised 1/5/17

BALD EAGLE NEST CAMS

The pages I have published under this tab (Bald Eagle Nest Cams) as well as elsewhere on the website, present information I have gathered from  Judy Barrows’ charts, the Hancock Wildlife Forum, the Channel Islands EagleCAM Forum, the Hornby Eagle Group Projects Society forum, individual nest cam websites, numerous Facebook pages and groups, and my own observations.

Here you will find: