A duck built for eggs
Mrs Adele Campbell introduced the breed in 1901 in Gloucestershire, England [1]. Kentucky Extension says she crossed a Runner with a Rouen, and then crossed the offspring with Mallards to add hardiness, with the aim of a duck that laid well but had a bigger body than a Runner [3]. Metzer says she was adamant that her birds were for production, and that the breed has since been developed into an exhibition type as well [1]. The Livestock Conservancy lists it on its Watch list [4].
Looks
There is one variety: khaki [3]. Metzer adds that the breed was initially a fairly mixed-colour duck and that breeders later settled on the khaki colour [1]. It is a light-class duck, small compared with the Pekin or Rouen: hens are about 3½ to 4 pounds and drakes 4 to 4½ [3].
Eggs
Egg production is the reason to keep them, and the figures are the most variable of any breed we have covered. Kentucky Extension's table says 200 to 300 eggs a year [3]. Metzer's table says 165 to 240 for its breeders, with the upper figure assuming artificial light [2]. Metzer's own page quotes far higher numbers, 335 to 340 eggs in 365 days from a 1950s flock and 346 from a single bird, citing the Jansen flock standards [1]. Those are historic figures from one selected flock and one individual bird, so we treat them as a ceiling for what the breed has done, not a promise. Kentucky Extension says Campbells can lay an egg a day for ten months [3], that the egg is off-white [3], and that using lights lets them lay through the winter [3].
Temperament
Both our sources describe an edgy duck. Kentucky Extension says Campbells and Runners tend to be nervous and flighty and will stampede when startled [3], and Metzer scores Khaki Campbells 9.0, the top of its scale of 1 to 9 [2]. That does not mean every individual is jumpy, and a duck raised by hand usually settles, but if you want a placid lap duck this is not the breed to start with. Kentucky Extension also notes that they seldom go broody, because broodiness was sacrificed for egg production [3], though Metzer rates their mothering as good [2].
Foraging and flight
Kentucky Extension lists Campbells among the best foragers, along with Magpies, Runners and bantam breeds [3], and Metzer rates their foraging as very good [2]. On flight we have only Metzer's "Maybe" [2], so check your fencing rather than assuming.
What we have not pinned down yet
We have no source we trust for how loud Khaki Campbells are, how long they live, or how they cope with heat and cold. Customer reviews on Metzer's page describe their quacking as excited and mention frozen water problems, but individual reviews are not evidence, so those rows are blank.