Duck Winter Light Planner: Day Length, Hours to Add and Timer Times

Put in a latitude and a start date and the planner works out the natural day length there, how far short of a laying day it falls, and a timer schedule that builds the light up gradually — winter lighting for ducks done the way the hatcheries and the universities describe it. The hours and schedules come from Metzer Farms, Cornell’s Duck Research Laboratory, North Carolina State and the University of Georgia, with Penn State and Maine’s hen guides for comparison; the sunrise and sunset arithmetic is NOAA’s.

Key takeaways

• Metzer Farms says an increasing day length from 21 December to 21 June stimulates ducks to lay more and the shortening days after 21 June to lay fewer, so laying tails off in autumn without lights.
• The duck sources give 14 to 17 hours of light: Metzer brings its breeders to 17, Cornell gives 14–17, Georgia 14, and North Carolina State 14 then 16.
• Build up gradually: Metzer adds three-quarters of an hour at each end of the day, then half an hour every three or four days; NC State adds 30 minutes a week.
• Once the lights are on, the lit day must never get shorter — Cornell, Penn State, Maine and Georgia’s backyard hen guide all say so — and Metzer holds its timer at the longest natural day of the year.
• Do not light ducks under about 20 weeks: Metzer starts at 20–23 weeks, NC State at 22, and Georgia says not before seven months.

Why day length decides when ducks lay

Ducks run on the calendar. Metzer Farms puts it plainly: an increasing day length from 21 December to 21 June stimulates birds to lay more eggs, the shorter days after 21 June stimulate them to lay fewer, and controlling day length is what starts, maintains and stops production. Cornell’s Duck Research Laboratory agrees: without supplemental light, production is seasonal and follows the natural day. eXtension’s breed guide says that with a lighting system, Campbells lay through the winter months, and notes that ducks lay most of their eggs within three hours of sunrise, against five for chickens — worth knowing when you plan collecting the eggs.

Geese are the exception. Metzer’s second lighting article says nobody in North America photo-stimulates geese, because lit days of 13 hours or more depress their laying; the most eggs come from days of no more than 10–11 hours. This planner is for ducks.

How many hours, and from what age

The published duck targets sit between 14 and 17 hours, and the planner offers the four figures the sources give:

• Metzer Farms brings its breeders to 17 hours of light and 7 of dark, and says ducks need at least 17 hours to lay continuously all year.
• Cornell says extending the day to 14–17 hours, and preventing any decrease, lets ducks lay continuously for 7–12 months depending on the bird; its worked example is 14 hours of light and 10 of dark.
• North Carolina State’s breeder duck programme goes to 14 hours at 22 weeks and 16 at 24, and says not to exceed 16 unless the natural day where you are is longer.
• The University of Georgia’s duck guide says ducks can be brought into full production with 14 hours of light a day once sexually mature.

The hen guides from Penn State and Maine give 14–16 hours, so 17 is the top and 14 the floor; the result panel says where each figure comes from.

Age sets the start. Metzer begins once the birds are 20–23 weeks old, smaller breeds at 20 and larger at 23. NC State uses natural daylight until 22 weeks and warns never to rear young breeders on naturally increasing days or constant long lit days. Georgia says it is not desirable to bring ducks into lay before seven months, because of small eggs and low hatchability, and Cornell says light matters less for growing ducks, whose day length is best kept steady. The planner warns below 20 weeks.

Building up gradually, and which end of the day

None of the sources switches straight to the target. Metzer’s own breeders, started in December, get three-quarters of an hour before sunrise and three-quarters after sunset, then another half hour every three or four days, alternating morning and evening, until the day is 17 hours of light and 7 of dark. Its home-flock page is slower: half an hour at sunset and half an hour before sunrise, then another 45 minutes a week split between the two ends, up to 17 hours. NC State’s step-up, written for a breeder flock coming back into lay after a moult, adds 30 minutes a week to the natural day, morning one week and evening the next, until the first egg, then goes straight to 16 hours or the longest natural day.

On which end to add it, ducks and hens part company. Metzer and NC State alternate the two ends, and Cornell describes the usual practice for ducks shut in at night: lights on before sunrise and off after it, on again before sunset and off after it, so the light and dark periods stay constant. Penn State, writing for hens, adds the light in the morning and lets the birds go to roost with the natural sunset; Maine, also for hens, describes both ends but says that adding it all in the morning has that advantage, and suggests a dimmer if evening lights are used. The planner offers both ends or morning only, and rounds every timer time outwards to the quarter hour, because Metzer says the plug-in home time clock adjusts in 15-minute steps.

Never let the lit day shrink

Every source agrees on this one. Cornell’s 14–17 hours is conditional on “preventing any decrease in day length”. Penn State: “Never decrease the lighting period on birds in production, or they will stop laying.” Maine says “Laying birds must never see a drop in day length.” Forget a hand-worked switch for one day, it adds, and production may drop, which is why it calls a timer a necessity. Georgia’s backyard lighting guide says birds never exposed to a decreasing day length should not stop laying abruptly mid-cycle.

Metzer turns the rule into a timer setting: increase the lit day to equal the longest day of the year at your latitude, so the ducks “never notice the days getting shorter” after 21 June. Metzer’s own clocks run lights off at 9:30pm and on at 4:30am. NC State says the same another way: if your natural day is longer than 16 hours, set the time clock to match it. The planner’s hold-there times do this for any latitude between 65° north and south: fixed lights-on and lights-off times, the target centred on solar noon but stretched, whenever the natural day beats it, to run from a quarter hour before the earliest sunrise of the year to a quarter hour after the latest sunset, so the timer never needs touching again. The month-by-month table lists sunrise, sunset, day length and the hours to add, and the planner marks the dates the natural day drops below your target and climbs back above it.

Brightness, bulbs, timers and fire

The light does not need to be bright. Metzer says as little as half a foot-candle works, 3–5 foot-candles is probably better, and in general that means “sufficient light to read a newspaper”. Cornell says about 10 lux, one foot-candle, at the duck’s eye level is sufficient, and NC State wants one foot-candle at the height of a duck’s head, adding that “One footcandle is actually very dim light.” On bulbs, Metzer says a single 100-watt incandescent is enough for a small flock, and two smaller lights beat one big one in case one burns out; Georgia says a 40 to 60 watt bulb; Maine, for hens, a 60-watt incandescent, a 14-watt compact fluorescent or a 9-watt LED per 200 square feet.

Metzer describes two kinds of timer: an industrial time clock wired into the circuit, adjustable by any amount, and the plug-in home type with a minimum adjustment of 15 minutes. Maine says to check a lone bulb daily and the timer weekly, and gives one plain warning: incandescent bulbs get hot, so keep fire prevention in mind when wiring the house, and always hang a heat lamp on a safety chain. Keep the bulbs clean; the duck house guide covers the building itself.

Darkness, a gentle switch, or a rest

Every plan here still leaves a night: Metzer’s 17 hours leaves 7 hours of darkness, Cornell’s worked example 10. The RSPCA’s welfare standard for commercial duck farms asks for at least 6 hours of continuous darkness in every 24, no intermittent lighting to make up those hours, dawn and dusk periods, and artificial lights switched on and off in a stepped or gradual manner over at least 20 minutes. The DEFRA welfare code for ducks says birds should be accustomed to the dark, with dimmers or other devices to avoid sudden changes.

It is also reasonable not to light at all. Metzer turns the lights off when it wants a flock to moult and rest, and Georgia says some keepers moult the birds for 8–10 weeks for a second laying period. A winter off is a choice, not a failure. What the sources rule out is the half-measure: lights that come on some days and not others, or a lit day that creeps shorter.

How the day length is worked out

Sunrise, sunset and day length are calculated in your browser the way NOAA’s sunrise and sunset calculator does it: the Meeus-based algorithm its Solar Calculation Details page describes, with the sun’s upper edge crossing the horizon at a zenith of 90.833°, which allows 0.833° for refraction and the size of the disc. NOAA says the results are “theoretically accurate to within a minute” between 72° north and south, that what you actually see can differ from the calculation because of the atmosphere, and that the error grows the further you are from the equator, because the sun then rises and sets at a shallow angle; the planner works between 65° north and south only. We checked the script against an independent implementation of the same algorithm across 87 place-and-date cases, identical to the minute in every one, and against published sunrise and sunset times for London, New York, Sydney and Reykjavik, within a minute. Day length needs only a latitude; clock times need a longitude too, shown in your device’s time zone. The Use my location button asks the browser for permission and only fills the two boxes; nothing is stored or sent anywhere.

What to do with the plan

Lighting changes the laying forecast, so the planner hands its lights setting to the egg production calculator, which has the same switch. If your ducks have not started yet, when do ducks start laying eggs is the guide to read first. The feed calculator gives the daily ration for the flock you are lighting, and keeping ducks in winter covers the rest of the season’s care.