New Zealand Gillham left London by boat on 19 November 1956, arriving at New Zealand on 22 December 1956, after 33 days of sailing (stopping at Curaçao, Panama and Pitcairn on the way). She spent much of her time here studying New Zealand's natural history, especially the bird life. Whilst in the North Island she paid visits to Auckland, Palmerston North, Wellington, Napier and Cape Kidnappers; studying the Gannet colonies at the latter. On 12 January 1957 she then moved to the South Island, visiting multiple locations including; Dunedin, Otago Peninsula to study Albatross colonies, Green Island, Southland, Fiordland, Stewart Island to look at the Muttonbird colonies, Muttonbird Island, Christchurch, Hokitika, Westland, Nelson and Picton. Gillham moved to Massey, where she moved into Moginie House to begin her one-year Botany exchange lectureship and wardenship at
Massey University on 27 February 1957. and later headed to Wellington on 9 May 1957 where she spent time at the Animal Ecology section of the
Department of Scientific and Industrial Research. Later that year in August Gillham visited Auckland, from which she travelled around the Hauraki Gulf visiting Mokohinau, Little Barrier and Rangitoto Islands. When back in Massey, she attended the New Zealand Ecological Society annual conference on 29 August 1957, where she discussed her research paper "Ecology of some New Zealand seabird colonies".
Australia Gillham left Auckland by air for Sydney, Australia on 21 December 1957, also visiting Canberra and Corowa in the following days. She began an exchange lectureship working as a Senior Demonstrator at the Department of Botany at the
University of Melbourne on 3 March 1958. She later visited these islands again in December 1958, with the addition of
Tucks, West, East and South Spences, Little Green,
Penguin Islet, Apple Orchard and Samphire. On 25 April 1958 Gillham then set out for a visit to Phillip Island, to see and learn about the
koalas on the Island and the
little penguin colonies at
Phillip Island Nature Park, or 'Penguin Parade'; visiting the Island again later that year in October to collect penguin guano for the Microbiology Department at the University of Melbourne. Gillham joined a McCoy Society trip to
Chinaman Island on 10 May 1958, in the north-west corner of
Western Port, where she created lists of the Island's grazed and ungrazed plants. Later that month Gillham also holidayed at Albury, moving to Sydney, Kempsey and then to Brisbane. She then also paid visits to
Lone Pine Koala Sanctuary,
Lota, the
Moreton Bay islands and
Enoggera Reservoir. She took a trip to
Cape York, leaving Melbourne by boat a year later on 12 March 1959.
Tasmania On 7 February 1959 Gillham left for a Tasmanian tour. She also spent the three summers of 1958–1960 at Tasmania investigating (as part of a team) the costs and benefits of pastoral farming and
muttonbird harvesting, residing at a research hut on Fisher Island, in the Eastern Bass Strait between Tasmania and mainland Australia.
Macquarie Island In December 1959 Mary Gillham, along with Susan Ingham (British),
Hope Macpherson and
Isobel Bennett (both Australian), became the first female scientists to join a research trip to Macquarie Island, Antarctica with ANARE (Australian National Antarctic Research Expedition). The success of these ground-breaking women during this trip paved the way for more female scientists to be able to join future expeditions such as this; had it not turned out so well, the involvement of female scientists on research trips would have been greatly delayed.
Africa South Africa Following her travels in Australia Gillham travelled to South Africa, arriving at
Cape Town by boat on 1 May 1960. On 8 May 1960 she moved to Saldanha, from which she took an expedition to three of the Saldanha Bay Islands; Jutten, Malgas and Marcus. Gillham headed back to Cape Town on 13 May 1960, where she spent time at Compton Herbarium and visited Cape of Good Hope Nature Reserve. On 24 May 1960 Gillham visited Robben Island, and a few days later she then left for a bird-watching trip at Lambert's Bay. Gillham joined a two-day trip to Port Elizabeth on 1 June 1960, which she visited again later that month. She also took two trips to both Meeuw Island and Schaapen Island later in June that year. She left Cape Town for Pretoria on 26 June 1960, stopping at Karoo, Parys and Johannesburg during the journey.
Central Africa Gillham joined a day trip to Mozambique on 7 August 1960 where she visited the Susengenga (Little River Research Station); an agricultural research station, and the Barragem Oliveira Salazar dam. From here, she travelled to Sabi Valley, to Fort Victoria (now called
Masvingo), back to Johannesburg and then reaching the Congo (after travelling through Angola) on 12 August 1960. Between 27 January and 5 February 1994, Gillham spent time travelling around Zimbabwe, as well as spending a full day in Botswana, joining a sail along the River Chobe boundary of Namibia and also participating in a walk across Victoria Falls bridge to Zambia.
Nigeria After Gillham's visit to Central Africa in August 1960, she travelled to Ghana on 12 August, but leaving on the following day (13 August) via
Nigerian Airways to get to Lagos, Nigeria. On 14 August 1960 she arrived at Ibadan where she paid visits to tropical forests and the
Olokemeji Forest Reserve. Later that month she also travelled to Minna, Nigeria from Jebba railway station to see the savannah zone. She also visited Kano in the same year, where she took a photograph of the
Great Mosque of Kano.
Aldabra Island In 1970 Gillham took a sabbatical to carry out research on
Aldabra (CORR) in the
Seychelles; far out in the Indian Ocean and virtually isolated from human activity. The US military wanted to turn the island into an airbase, therefore Gillham was to report information about the island's wildlife back to the
Royal Society and the
Smithsonian Institution before building could commence. Gillham reported the importance of the island for sea birds, including
Frigatebirds, as well as for the
Aldabra giant tortoise, so the island was never built upon. Today it is listed as a
World Heritage Site. ==Achievements, awards and recognition==