  Primordial Black Holes (PBHs) are gravitationally collapsed objects that may
have been created by density fluctuations in the early universe and could have
arbitrarily small masses down to the Planck scale. Hawking showed that due to
quantum effects, a black hole has a temperature inversely proportional to its
mass and will emit all species of fundamental particles thermally. PBHs with
initial masses of ~5.0 x 10^14 g should be expiring in the present epoch with
bursts of high-energy particles, including gamma radiation in the GeV - TeV
energy range. The Milagro high energy observatory, which operated from 2000 to
2008, is sensitive to the high end of the PBH evaporation gamma-ray spectrum.
Due to its large field-of-view, more than 90% duty cycle and sensitivity up to
100 TeV gamma rays, the Milagro observatory is well suited to perform a search
for PBH bursts. Based on a search on the Milagro data, we report new PBH burst
rate density upper limits over a range of PBH observation times. In addition,
we report the sensitivity of the Milagro successor, the High Altitude Water
Cherenkov (HAWC) observatory, to PBH evaporation events.
